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Comment by silisili | Hacker News Reader

I'm not sure that would always help. I'm allergic to grasses and dogs, for example, despite growing up in a house with dogs and tons of grass outside.

I still love both, so just deal with it. Perhaps just exposure to more deadly things, like nuts and shellfish?

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Everything you're allergic to is something you were exposed to at least once; your immune system has to see it and learn to recognize it before you can react to it. Some types of exposure are good and some are bad.

Good types include oral exposure and continuous exposure (as in sublingual immunotherapy). Bad types include skin exposure (especially with eczema) and intermittent exposure with long periods of zero exposure (e.g. seasonal pollens including grass). Timing is also important especially relative to other immune triggers like actual sickness or vaccines or allergens that you already react to.

This is all poorly characterized in general and a lot more study is needed, but we definitely know of ways to expose you to allergens that are much less likely to cause allergies and in fact are likely to reduce or cure them.

> Everything you're allergic to is something you were exposed to at least once; your immune system has to see it and learn to recognize it before you can react to it.

Is this true? From a biochemistry perspective, it doesn't seem like it's necessarily true. Allergies could be genetic, in which case a genetic mutation results in the phenotype where an immune system mis-identifies allergens as harmful.

In biology anything is possible. I'd never rule out something like that. But for all common allergens I'm aware of it is true, you cannot be allergic until after your first exposure. That said, some things are "cross reactive" due to similar proteins, meaning that e.g. you could be allergic to goat's milk even though you've only been exposed to cow's milk. And some of these relationships are less obvious, like cashew and mango or banana and latex.

How do you detect that someone is allergic without exposing them? Or does the test not count? My tautology hackles are raised.

IgE tests can detect allergies without exposing the patient to the allergen. But they are imperfect. The only true test is exposure.

The test counts as a first exposure. But the reaction can only occur on a second exposure. I've often wondered if allergy tests can cause an allergy and while the allergists I've talked to don't seem to think so, I honestly don't see why not. So I would not suggest getting any unnecessary allergy tests.

If you will expose yourself to a substance, you will probably expose yourself to it hundreds of times. E.g. if you eat mussels at all, it might be something you eat now and then throughout your life. If each exposure has a certain probability of causing an allergy to the substance, then every individual exposure has a negligible risk.

Therefore, there is nothing extra risky about making the first exposure an artificial (but guaranteed to be safe) test, if you think you might be exposed in the future for any reason. In return for a negligible additional risk, you get a opportunity to discover if you are susceptible to an allergy before ever trying the substance. What am I missing here that leads to your advice of not "getting any unnecessary allergy tests"?

There are many cases that come to mind where someone has not been exposed to a potential allergen (growing up being sheltered from it, childhood aversion to it that was never reassessed in adulthood, simple lack of that allergen in previous environments) and I think it’s fair to want to avoid someone suddenly having new allergic reactions, especially when those reactions can “suck”.

My doctor says that tests can cause allergies and is therefore hesitant to give any kind of "test for everything" prick test (the ones with exposure by small cuts in your arm or back). In layman's terms as far as I've understood it, any allergic reaction, but also stress, infection, or environmental factors will get your immune system into a "alerted, defensive" state where it will learn currently present substances as things it will have to fight in the future. This can also include substances on your allergy test that are negative atm, but will be positive in the future because one currently true positive on the test aggravated your immune system.

So prick tests are a risk and you should never just blindly test, rather do the minimum necessary test for what you suspect will be positive, and only if an allergy is suspected anyways and serious enough to warrant the risk of testing.

> Is this true?

Yup! https://en.wikipedia.org/wiki/Allergy#Pathophysiology

“Everything you're allergic to is something you were exposed to at least once”

If you’re saying first exposure is what triggers/causes the allergy, I don’t believe this is true. Some people find out they’re allergic to penicillin the first time they get a dose. If they’re very unlucky it’s fatal.

The mold that produces penicillin is common indoors. It doesn't take a lot of exposure.

That's a type II hypersensitivity (IgM or IgG antibodies starting the complement cascade) and it's different from type I allergies (IgE causing mast cell degranulation). Type IV (cell-meditated, lymphocyte reaction) hypersensitivity, like poison ivy, is also different.

And then there's a whole bunch of other hypersensitivities that are poorly understood, like atopy.

An allergist I saw had four dogs walking around the clinic all the time. I asked him if that was a problem and he said in his experience, people aren't allergic to dogs, i.e. dander, but rather to the allergens that rest in the fur. Wiping the dogs frequently allows his patients to enjoy the company of the dogs. They were all short haired single-coated dogs.

The saliva, on the other hand, definitely can cause me to break out when a dog's teeth scrape my arm. But if I work with a cat and touch my eye, I get conjunctivitis right away.

Anyhow, the immunotherapy can really work, and definitely made my allergies better, even though it didn't ban them completely. For example, I used to be unable to share a room with a rabbit without an N95. Now I can visit rabbit households without a problem. My children will definitely be getting early allergy testing and immunotherapy if needed.

Anecdotal: Cat allergy shots helped my symptoms in a way that living with cats for years never did.

Never tried dogs. I did grass allergy shots for about 6 months as an adult. All that ever gave me was an itchy arm. My nose -still- becomes a spigot every time I have to cut grass...

6 months? Were you told to expect results that quickly? I don't think I saw meaningful results from my subcutaneous allergy shots for 1-2 years.

To be honest, no. I stopped due to out of pocket costs and not seeing any result in that time period.

I’m the same way. I tried the shots for a year but they made my eczema a lot worse. I wish they were a panacea.

6 months may not have been long enough for them to work. And allergy shot protocols are not standardized. Your allergist may not have used a large enough dose or the right updosing schedule. I've had shots at three different allergists (I stopped the first two treatments for personal reasons unrelated to the treatment), and this third one seems to give larger doses (which unfortunately makes the shots more painful), and is also the most effective one by far.

It took about a year before there was any noticeable effect for me. It was only at the 3 year mark when I could tell specifically how much better certain things were.

It it definitely not a quick fix, you need to commit to the long haul.

Edit Yeah, doing out of pocket definitely makes it harder to keep up with. Fortunately my insurance covers most of the cost of my shots.

There are broad-spectrum allergy shots that work by essentially turning off the part of your immune system that triggers allergies (IgE antibodies) while leaving the rest of your immune system (IgG, IgM, etc.) intact. I've been on one called Xolair for almost four years now and it's worked wonders for my copious environmental allergies... dust bunnies hardly make me sniffle now!

> I'm allergic to grasses and dogs, for example, despite growing up in a house with dogs and tons of grass outside.

I believe ramping up exposure dose is an important part of the protocol. You don't immediately jump to the highest dose for many drugs. Exposure to large amounts of allergens regularly just trains your immune system to continue responding as if it's being attacked. The point is to introduce doses that don't trigger a strong reaction so the system learns to ignore it, and then ramp up from there.

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