A discussion on immunity

[Paul B]

Did you read Paul's thread on slime that I linked? I'm pretty sure he has some sources on there. You've said a couple times now, in a round about way, that slime can't kill pathogens. It can.

I actually did post some links about this because contrary to popular opinion of just about everyone, I don't make this stuff up as I go along. OK, most of the time I do but being I amnot a scientist, but an electrician with an active imagination I did do plenty of research before I embarked on a subject that I realized the vast majority of people on here do not believe. Here is part of that I discovered but there is an enormous amount of new findings on the immunity of fish especially their skin.

If you are in a reading mood, you can find a lot of it here https://www.hindawi.com/journals/isrn/2012/853470/abs/

Quote:
ISRN Immunology
Volume 2012 (2012), Article ID 853470, 29 pages
http://dx.doi.org/10.5402/2012/853470
Review Article
An Overview of the Immunological Defenses in Fish Skin
María Ángeles Esteban
Fish Innate Immune System Group, Department of Cell Biology and Histology, Faculty of Biology, University of Murcia, Regional Campus of International Excellence “Campus Mare Nostrum”, 30100 Murcia, Spain

Received 26 August 2012; Accepted 12 September 2012

Academic Editors: A. Bensussan, E. Flaño, J. D. Hayball, and P. Puccetti

Copyright © 2012 María Ángeles Esteban. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract
The vertebrate immune system is comprised of numerous distinct and interdependent components. Every component has its own inherent protective value, and the final combination of them is likely to be related to an animal’s immunological history and evolutionary development. Vertebrate immune system consists of both systemic and mucosal immune compartments, but it is the mucosal immune system which protects the body from the first encounter of pathogens. According to anatomical location, the mucosa-associated lymphoid tissue, in teleost fish is subdivided into gut-, skin-, and gill-associated lymphoid tissue and most available studies focus on gut. The purpose of this paper is to summarise the current knowledge of the immunological defences present in skin mucosa as a very important part of the fish immune system, serving as an anatomical and physiological barrier against external hazards. Interest in defence mechanism of fish arises from a need to develop health management tools to support a growing finfish aquaculture industry, while at the same time addressing questions concerning origins and evolution of immunity in vertebrates. Increased knowledge of fish mucosal immune system will facilitate the development of novel vaccination strategies in fish.

 

[Brew12]

It's funny in a way to see one "side" say that QT is not enough.

And then it's funny in a way to see the other say that supporting the immune system is not enough.

Doesn't the disagreement part feel a bit contrived? It does to me. There's no actual disagreement in there.

It sounds like you are changing your argument. I have never seen you recommend or support 100% QT. I don't think anyone would argue proper nutrition isn't important. We have an entire section on this forum dedicated to nutrition now. If you are saying you support 100% QT you have a strange way of showing that support.

I've looked through the first page of search results and none of them mentioned eradication of uronema. The only ones I have seen discuss reducing mortality rate. Can you link the actual study instead of the search results?

 

[Brew12]

I actually did post some links about this because contrary to popular opinion of just about everyone, I don't make this stuff up as I go along. OK, most of the time I do but being I amnot a scientist, but an electrician with an active imagination I did do plenty of research before I embarked on a subject that I realized the vast majority of people on here do not believe. Here is part of that I discovered but there is an enormous amount of new findings on the immunity of fish especially their skin.

This is an excellent article and one I have read before when you referenced it. I highly encourage anyone interested in this subject to read it. These are some excerpts.

"The skin and gills are common sites of parasite infestation despite the barrier functions associated with mucosal epithelia of fishes. To resist or minimize the impact of parasite infection, both innate and adaptive defence mechanisms have to be involved (reviewed by [285])."

"Mucus, as it has been underlined, plays a role in limiting the parasite load [290]. Monogenean and crustacean ectoparasites modulate mucus production during attachment by reducing the density of mucous cells in the skin of the host [291, 292]."

"Non-parasitic fishes usually die following infection, but animals surviving sublethal parasite exposure become resistant to subsequent challenge. This resistance correlates with the presence of humoral antibodies in the sera and cutaneous mucus of immune fishes."


Mucus is very important to both the innate and adaptive immune systems of fish. However, as this article describes, the initial exposure to the parasite must be sublethal. In the open ocean, this can occur because of dilution. In an enclosed system there needs to be something else that limits parasite numbers to keep the initial exposure sublethal so that the adaptive immune system can develop. This is where the ozone or UV filter comes in to play. Once the adaptive immune system is in place, it will limit the parasite load and the UV or ozone will no longer be required.

 

[Paul B]

That article is the essence of my system and practices. People who don't believe in immunity won't read, understand or believe that which is the reason for all the disease posts.
There are numerous articles on the subject that say basically the same thing.

References:
Me

 

[Brew12]

That article is the essence of my system and practices. People who don't believe in immunity won't read, understand or believe that which is the reason for all the disease posts.
There are numerous articles on the subject that say basically the same thing.

References:
Me

Yup. And if people would follow your system and practices, and actually understand them, hobbyists would be much better off. The problem is when someone tries to pick and chose the parts of what you do that they want. If they don't do something to limit the number of parasites in the system when the fish are developing their immunity to each new pest they encounter they are relying on luck. If they follow your system they can be confident that they will have success.

 

[mcarroll]

It sounds like you are changing your argument. I have never seen you recommend or support 100% QT. [....] If you are saying you support 100% QT you have a strange way of showing that support.

Now there's the Eradication'ista in you talking!

You are correct in that I am not fanatical about them. That means I can see both the good in them and the bad in them.

I'm an "appropriate use of technology" kind of guy so you don't typically find me getting fanatical about things that I can understand.

QT's have their place and in so many words that's all you've ever seen me say.

I think I even specified a few posts ago what I don't like about some QT recommendations:

Some wellness recommendations we read on here and elsewhere don't account for the immune system, or even outright deny its role. Putting an apparently healthy fish prophylactically into a 10 Gallon PVC-decorated QT for 3+ months with copper would be one stereotypic version of this recommendation which illustrates most of the bad points a recommendation can have. The only way to make it worse is to make the example fish a Tang.

I hate to say it, but there are bad ways to QT, there are bad times to QT, there are bad fish to QT. QT is not a cure-all, it's not a panacea and outside of laboratory/boy-in-a-bubble-like circumstances (70's reference), it's not capable of eradication Eradication. I'm sorry.

Any big place like a farm or aquarium or zoo that cares, uses QT. But they never ever end it there.....it's just a tool.
They have very elaborate biosecurity protocols surrouding the QT system, for example....many of which we can't practically duplicate.
They never ever seem to have a conversation about disease without talking about what stresses they could eliminate or what aspects of diet could be improved. Literally every disease guide I've read has this very complete focus. QT is part of it, but a tiny part.

There are appropriate uses of QT, but only in the context of a system designed for maximizing all aspects of fish immunity – even during QT.



Another good article (c. 2011, so pretty current)....you have to sign up for a jstor account (free) to see the whole thing:
FISH QUARANTINE: CURRENT PRACTICES IN PUBLIC ZOOS AND AQUARIA

Not nearly as telling as I wanted it to be so I haven't gotten around to putting it on my blog yet, but still a really good read.

 

[Brew12]

You are correct in that I am not fanatical about them. That means I can see both the good in them and the bad in them.

I can see the good and bad in them also. I only realize that the good outweighs the bad for the way most hobbyists run their systems.

I'm an "appropriate use of technology" kind of guy so you don't typically find me getting fanatical about things that I can understand.

Picking and choosing what you like isn't "appropriate use of technology". You can't pick and choose which parts of Paul B's method to use and expect it to work the same way. You can't QT some fish some of the time and expect to have a healthy system.

I hate to say it, but there are bad ways to QT, there are bad times to QT, there are bad fish to QT. QT is not a cure-all, it's not a panacea and outside of laboratory/boy-in-a-bubble-like circumstances (70's reference), it's not capable of eradication Eradication. I'm sorry.

Science says otherwise. It is absolutely possible to eradicate common pathogens through solid QT practices. There are scientifically proven methods that we know will eradicate Crypto, Velvet, Flukes and internal parasites. It takes dedication but science shows us how to do it.
And we are not trying to create a boy-in-a-bubble situation. Once in a DT they are exposed to a wide range of bacteria and micro fauna. The only thing proper QT and prophylactic treating does is eliminate fish based parasites.

Any big place like a farm or aquarium or zoo that cares, uses QT. But they never ever end it there.....it's just a tool.
They have very elaborate biosecurity protocols surrouding the QT system, for example....many of which we can't practically duplicate.

QT is only a tool and the first stage of a complete method of maintaining a system. It is a tool that does no good if it isn't used and used appropriately. For larger fish farms and aquariums, they rely on having a certain percentage of die off when they QT a new supply of fish. They will then do a full examination of the fish and treat the remaining fish appropriately. This is beyond the ability of most hobbyists but is done by commercial ventures because it is a cost trade off. The communications I have had with people who run smaller aquariums seem to lean toward prophylactic treatment.

 

[mcarroll]

I only realize that the good outweighs the bad for the way most hobbyists run their systems.

You may keep thinking this distinguishes an Eradication'ista but it does not.

What distinguishes us (I'm repeating) is that non-Eradication'istas think there can be a wrong way, wrong time and/or wrong fish to quarantine. We are not fanatical about it.

In the right circumstances, it's the right thing to do. That's it. No 76 day miracles. No unrealistic claims.

If someone thinks they need to QT all their purchases or not QT all their purchases, who am I to argue without knowing a lot more about the situation?

In contrast, the Eradication'ista usually has a prescribed course of action which gets handed out before they've even assessed the situation. I've seen whole recommendations based on little more than a photo or even a text description of the fish in question.

That would be like us treating disease by skipping the doctor and just visiting the pharmacy.

Picking and choosing what you like isn't "appropriate use of technology".

Appropriate use of technology means using what's appropriate when it's appropriate – based on the demands of the situation.

It does not mean using what you like when you like – based on your feelings.

And you're being generic when I was being pretty specific in my hypothetical from earlier.

Let me paraphrase here to keep the idea on track:

Someone trying to improve their tank by looking at Paul B's system and who then makes a list of 10 or 20 differences between their methods and Paul's, and then picks their 2-3 favorites from the list to emulate, is not going to go wrong.

You have to make them pick an absurd combination of items to even have a questionable example to show.​

It is absolutely possible to eradicate common pathogens through solid QT practices.

What's possible on paper, or in theory, or in a one-off by a focused individual, is different from what happens in reality, on average, over time, at home, with fish and with normal people.

Our reality is:

• Some QT's go wrong.
• Some organisms can't be easily or properly QT'd.

What happens to the Eradication'ista Plan when one or both of those factors must eventually be accounted for?

To compound the issues, most beginners go too fast in general and most people continue adding new things to their tank on a regular or semi-regular basis...each new thing being another chance for the QT to "go wrong".

There's no study I know of that's looked at people's tanks exactly like this, so that's mostly all my opinion...but time and human habit would both seem to be on my side.

People tend to make mistakes and life tends to find a way.

This is when your fish need their immune systems most.

High-quality food and high-quality environment are the two required paths to get it. (All my "pesky questions" in disease threads usually revolve around these two things.)

Everything else is extra. (Extra does not mean expendable....simply not required.)

QT is only a tool and the first stage of a complete method of maintaining a system. It is a tool that does no good if it isn't used and used appropriately.

I like!

You know one aspect of this which gets glossed over (and seems mostly forgotten) is this:

Your LFS is supposed to be the QT environment.

Moving a fish from their tank to yours should be a no-brainer. And it has worked like that for innumerable fish over the history of this hobby. (Still does.)

Even just in the 15+ years the store where I worked was in business, the numbers of healthy saltwater fish that were placed into healthy tanks was awesome! Mortality rates even in the shop were very, very low...mostly related to bags that didn't make it through the shipment process than due to anything else.

I only personally knew of 1 or 2 customers there that had a home QT system – but the vast majority had longstanding tanks, never having had a wipeout. (With mostly repeat customers, in retail, you get to know most of them pretty well!!)

Seasonal disasters/power outages were the only things that seemed to cause tank wipeouts for our customers. That was rare too though as we'd generally make sure people were prep'd.

(The store is a private service now and, for what it's worth, they still have the same "luck" with the fish....using the same methods, all while ordering the same fish as everyone else in the industry orders. Which brings me to...)

If you don't have a LFS, well that's a sign-o-the-times.....I don't either, anymore.

We're....ah...."dis-fortuned" now....IMO.

The option we now have is buying wholesale-quality fish (maybe worse) at retail cost.

You should have to go out of your way to bring home a sick fish from your LFS. Like ignoring them when they tell you the fish just came in. Or ignoring the other sick fish in the tank. Ignoring the fish's own behavior. Etc. You have a lot of control in this situation, you only need to exercise it.

Buying online, you have NO CONTROL. You're at the mercy of someone else who's going to ignore all those things for you since they have lots more orders to fill besides yours....AND they're going to throw your fish in a box and hand them over to a shipping company that's also delivering bowling balls, pencils and building supplies.

These fish do not get a happy QT in the store followed by a pleasant xx-minute trip home in your car with the AC or heat chugging.

When you're forced to shop online, caveat emptor totally applies...since you're buying sight-unseen and with the fish likely to be in rough condition on arrival. Your shopping is impaired.

In that case, you better be just as ready as a fish store would be.

That means:

• Adequate QT space – nothing skimpy.
• A QT that's properly equipped, and at least 10' from the display – UV for certain; maybe diatom filtration.
• Hospital facilities available, including at least one separate tank, a microscope and basic, common med's. Ideally isolated from the QT space and the display space by 10'.

As a beginner, I would hate to start out on the ocean of marine fishkeeping in such a rotten boat.

I think I would hesitate to advise many newbies to proceed with this course. Meaning, under that circumstance, I'd be likely to recommend no fish till they aren't newbies. Which is easy for me to say since most folks are already past this point when they ask someone else for help. Too late to say "Wait a little while!" That usually means they need husbandry info too....all of it, not just the chapter on QT and hospital (which they may want as well).

 

[Paul B]

Our reality is:

• Some QT's go wrong.
• Some organisms can't be easily or properly QT'd.Quote:

This is very true. I just now received this PM from a Gentleman in India:
Quote:
I mainly need it for my new copper band which is not eating artemia, PE mysis and shirmps. I am not having access to scallops in our local fish stores. So I have left with only the try for black worms. He is in QT and not started with any medicine. I am trying to make him eat and if not possible shall I put him in the display directly. What do you suggest ?
End Quote

Many people find copperbands to be a hard fish to keep. I don't find that but they are more finiky than most fish. But they are lousy quarantine inhabitants. A fish like a copperband, tang, angel, lookdown etc, would normally be so stressed in quarantine that I am sure the majority of them that are quarantined, don't last long. Fish like clown gobies, wrasses, bleenies etc, would do better because they don't normally swim very far. If you have ever followed copperbands, tangs or long nose butterflies on a reef you will see they need to swim hundreds of yards around their reef to find food and mates. Just look at the disease forum and see how many of those fish I mentioned died or never ate in quarantine.
I don't make this stuff up because I heard it on "The View" (God Forbid), I usually dive with the animals that I try to keep. I learned more in 15 minutes diving with Moorish Idols than I did in 20 years of reading about them mostly by authors who only know them by texting and never swam with them in their home.
I took these Bora Bora.





This is the harbor where I took those. This is also where they filmed "Mutiny on the Bounty" if anyone is interested. That is our ship

 

[Paul B]

I just started this thread which goes along with this discussion.
https://www.reef2reef.com/threads/the-importance-of-live-bacteria-in-food.300641/

 

[klp]

@Paul B I knew the story would be like that - direct parallels with the human-oriented research I've been doing. GREAT article.

After you eliminate the obvious differences between species, our immune systems are pretty much identical to fishes. Puss with active macrophages covering a human wound and the mucus covering internal skin, including the guts, are all the similarities to fish slime I need to consider. All that's missing is an ocean!

Just for the general interest and to put fish immune systems into perspective, from my favorite links thread, is this link and quote:
Microbial Food Webs

"Most of the biomass in the ocean is made up of viruses (Zimmer 2006)"

"There are more than 5,000 different types of viruses in 100 ml of seawater, and more than 1,000,000 in a kilogram of sediment (Rowher 2009)."​

All of these can be present on fish's slime - and be an enormous bio/pharmaceutical defense system.



Is this technically true?

I think one is better off thinking that they ARE part of the immune system. You cannot account for its function without accounting for them - trying would seem to be a mistake.

Just starting through this old thread and I get the error page "http://ocean.tamu.edu/error.htm" when clicking your link "Microbial Food Webs" which sounded fascinating. Can you get us a correct link if one still exists?

 

[Paul B]

lkp, I guess they took that site down. This is an old thread and I am on old Man so I don't know what happens to old links.
Mcarrol linked that so maybe you can ask him.

 

[mcarroll]

Just starting through this old thread and I get the error page "http://ocean.tamu.edu/error.htm" when clicking your link "Microbial Food Webs" which sounded fascinating. Can you get us a correct link if one still exists?

Yeah that's on my favorite links list too....noticed they took it down a while back, but there doesn't seem to be a replacement.

marine food web is a more accurate concept for us anyway, and there are tons of depictions, but none have been quite as perfect as the onde tamu.edu had posted.

 

[mcarroll]

@klp try this one:
http://www.icm.csic.es/bio/projects/zootransfer/rationale/ztrationale.htm
I can't explain the title, the the info on the page is great.

"Very simplified view of the main trophic pathways in planktonic food webs. Blue arrows indicate pathways of the so-called "classical food web". Orange ones are for the "microbial food web" (See explanation below)."

 

[Paul B]

That food web is largely missing in most tanks. I try to have a natural food web going but of course no where near as diverse as the sea. There is always something spawning in my tank being amphipods, crabs or fish and I feed new born brine shrimp every day. If I didn't there are many fish I keep that I would not be able to keep. And I am a big advocate of live foods for a successful tank.

 

[mcarroll]

+1

From GFO to carbon dosing to all the other even-more-bizarre treatments out there, it seems like that whole microbial food web (orange branch) gets a lot of abuse in our tanks – even if we're doing well enough to have a functional "classic" food web (blue branch).

 

[Paul B]

This morning my wife and I were discussing how we lived when we were much younger and how the world has changed. My Dad and her Dad had retail stores. My dad had a fish market and just like her dad and everyone with a food market there was piles of saw dust on the floor. The cutting boards were wood, the knife handles were wood and the fish, and meat came in wooden crates as plastic was not available then. I am talking about the fifties.
I used to play in the back yard of our fish market and shoot flies with a rubber band. We also had live carp and eels in old bath tubs.
At the end of the week my Dad would sweep the floor and throw out all the old, fish scale infested sawdust and put down clean sawdust. Every night he would clean, using soap and bleach the knives and cutting boards.

Today, you are not allowed to use saw dust, wooden handled knives or cutting boards probably because of lawyers. I am sure someone, some where got sick and saw dust was blamed just like coffee can't be hot any more.
But it was the saw dust, cutting boards and wooden knife handles as well as numerous other things that enhanced our immune systems.
I was always an out doors kid and cut myself many times. I would rinse it off in a puddle or pond and go about my business never thinking about it.
I had an uncle that worked at the docks in NYC, one of the roughest places on Earth at that time. He got stabbed in the belly twice when 3 guys tried to mug him. (the muggers didn't fare very well) My Uncle wrapped the wounds in the same rag he cleaned eels with and lived to be about 90 never seeing a doctor or dentist in his life.
When my Mom would get a cold as a kid, her Mother would make her sleep in the horse stables thinking the smell of horse poop would cure her. (my Mom was born in lower Manhattan in 1910) My Mother lived to be 99 years old, she died of old age and was never sick and never even took an aspirin. How many people today could say that?

The point of this is that today how many kids do you know with allergies? How many kids are allergic to peanuts? How many kids are home from school with colds?
How many people in their 60s or 70s can you name with allergies?
Probably very few. As a kid no one in my school had any allergies and we all ate peanuts. I always got an attendance award because I was never out sick. I think in the 40 years I worked as a construction worker in Manhattan I was out maybe 3 or 4 times from being sick and never for having a cold, allergy or anything else except maybe a broken bone or disk problem.
That is IMO because I was brought up in a natural environment surrounded by bacteria and never having access to that silly sterilizing hand spray that people today feel they have to take baths in.
I still almost never get a cold, flu or any silly infection.
The little kids in My Grand Daughter's school almost all have some sort of allergy. My Grand Daughter is allergic to everything and half the kids in her school are allergic to something. Peanuts are outlawed in many restaurants and schools.
Kids today, (Like fish) get all sorts of things and in some homes it is an adventure waking up to see if the kids have some sort of infection.

I feel this is a big problem in our fish tanks and the biggest cause of all the posts on disease threads.
This is also why I go to a muddy bay and collect mud to throw in my tank. If I didn't live by the sea, I would throw regular dirt in there as I did when I started my tank.
I also feel we have to start thinking of bacteria as a good thing instead of a bad thing.
Just my thoughts of course and not meant to be taken as fact. Just an observation that is obvious to anyone who is a lot older than most fish people.

 

[mcarroll]

You've got me thinking (as usual)...I may attempt a little dirt-dosing from my garden. It's been a twenty years or more since anything like a pesticide has been used and even amphibians and reptiles show up from time to time (and procreate) during the year....so I think the soil here is healthy.

 

[Paul B]

Ed, dump some of that dirt in there, don't be a Sissy, your fish will thank you.

Too many people are cringing when they read about dirt. A few weeks ago we were at a bar be cue at my friends house and my Daughter's friend had here baby there. I saw the baby on the grass eating grass and dirt so I told her Mother who is a school principal. She surprised me by saying, I don't stop her from doing that because I want to boost her immune system. Now that Mom is 38 years old and I was so surprised to hear that answer. I mean, I believe it but most young people go crazy if they see a baby put something dirty in their mouth.
If you go to a museum, look at the cave Man exhibit and see if you can see any of them holding that sanitizing hand spray. In most cases you won't see that and cave men (and girls) got along just fine. The ones that died young was because of that saber tooth tiger problem they had and the fact that if they wanted a hamburger, they had to take down a 2,000lb mastodon using a stick and harsh language.

Kids growing up today are in big trouble which is why you can't get an appointment to see a doctor for 6 months. So many more people are sick these days and we didn't get any of this stuff.
It's hard to cut yourself or get dirty playing with an I Pad inside a sterile house or texting your friend about a new Net flex movie or computer game.

We used to go to this lot that had construction debris in it and throw 8' fluorescent tubes at each other. They smashed all over us and so far, no one got cancer or glows in the dark. We also had a rope swing there where most of us broke an arm or leg, but never got sick. I would wade through huge puddles in the mud catching tadpoles then drink the water from the lake. Never got sick.
I spent a year in the jungle in Nam, never got sick.
Every few months we would get hot ice cream and it would be melted in the bottom of the canvas that was slung below a helicopter. We would push away the gunpowder, bugs, mud, and lizzards and scoop out the ice cream with our helmts and drink it as that was a treat. Never got sick.
I did lose my hair but many real Men don't need hair. I'm bringing Sexy back.

 

[eatbreakfast]

This morning my wife and I were discussing how we lived when we were much younger and how the world has changed. My Dad and her Dad had retail stores. My dad had a fish market and just like her dad and everyone with a food market there was piles of saw dust on the floor. The cutting boards were wood, the knife handles were wood and the fish, and meat came in wooden crates as plastic was not available then. I am talking about the fifties.
I used to play in the back yard of our fish market and shoot flies with a rubber band. We also had live carp and eels in old bath tubs.
At the end of the week my Dad would sweep the floor and throw out all the old, fish scale infested sawdust and put down clean sawdust. Every night he would clean, using soap and bleach the knives and cutting boards.

Today, you are not allowed to use saw dust, wooden handled knives or cutting boards probably because of lawyers. I am sure someone, some where got sick and saw dust was blamed just like coffee can't be hot any more.
But it was the saw dust, cutting boards and wooden knife handles as well as numerous other things that enhanced our immune systems.
I was always an out doors kid and cut myself many times. I would rinse it off in a puddle or pond and go about my business never thinking about it.
I had an uncle that worked at the docks in NYC, one of the roughest places on Earth at that time. He got stabbed in the belly twice when 3 guys tried to mug him. (the muggers didn't fare very well) My Uncle wrapped the wounds in the same rag he cleaned eels with and lived to be about 90 never seeing a doctor or dentist in his life.
When my Mom would get a cold as a kid, her Mother would make her sleep in the horse stables thinking the smell of horse poop would cure her. (my Mom was born in lower Manhattan in 1910) My Mother lived to be 99 years old, she died of old age and was never sick and never even took an aspirin. How many people today could say that?

The point of this is that today how many kids do you know with allergies? How many kids are allergic to peanuts? How many kids are home from school with colds?
How many people in their 60s or 70s can you name with allergies?
Probably very few. As a kid no one in my school had any allergies and we all ate peanuts. I always got an attendance award because I was never out sick. I think in the 40 years I worked as a construction worker in Manhattan I was out maybe 3 or 4 times from being sick and never for having a cold, allergy or anything else except maybe a broken bone or disk problem.
That is IMO because I was brought up in a natural environment surrounded by bacteria and never having access to that silly sterilizing hand spray that people today feel they have to take baths in.
I still almost never get a cold, flu or any silly infection.
The little kids in My Grand Daughter's school almost all have some sort of allergy. My Grand Daughter is allergic to everything and half the kids in her school are allergic to something. Peanuts are outlawed in many restaurants and schools.
Kids today, (Like fish) get all sorts of things and in some homes it is an adventure waking up to see if the kids have some sort of infection.

I feel this is a big problem in our fish tanks and the biggest cause of all the posts on disease threads.
This is also why I go to a muddy bay and collect mud to throw in my tank. If I didn't live by the sea, I would throw regular dirt in there as I did when I started my tank.
I also feel we have to start thinking of bacteria as a good thing instead of a bad thing.
Just my thoughts of course and not meant to be taken as fact. Just an observation that is obvious to anyone who is a lot older than most fish people.

If 'dirty conditions' were so prevelent 'back in the day' why didn't more people habe the longevity of your uncle and mother? They are still outliers, which speaks more to genetics than to exposure to germs.

If your personal immunity was more the 'norm' why did they give out an attendence award? Shouldn't perfect attendence have been commonplace according to your argument?

As far as allergies in kids today vs in the past there are numerous reasons, more than soley lack of exposure to germs at play. For one think more is known about allergies and how they present themselves in kids, from eczema, inflammation, and minor to serious digestive issues. Another thing, it is more socially acceptable to have allergies. Also, food packed in bph plastic, increased hormones and genetically altered foods, even how agri-giants have monicultured crops willall also be factors.