Like, is it when a small portion of a population has an adverse resction to something most of the species can handle just fine (i.e. a peanut allergy)? Or can it be a species thing? Like humans how get horribly itchy when the touch poison ivy, but other animal species eat the leaves and be just fine.
Would it be right to say that humans are allergic to poison ivy? If we’re not allergic, then is there another term for it?
Also, if it’s not an allergy, then where is the line drawn? I know there are a ton of people with pollen allergies, it seems pretty common. What percentage of the overall population makes an “allergy” a(n) [new term]?
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There is a classification system of hypersensitivity, the “Gell and Coombs classification,” that denotes 4 types of hypersensitivity. Type I hypersensitivity is considered an allergy, while types II-IV are considered different types of hypersensitivity. Type I hypersensitivity involves IgE antibodies and that’s what makes it unique. Other types involve different antibodies.
This classification system is somewhat antiquated and doesn’t have much clinical significance. The validity of it is debated and will likely change at some point.
TLDR: if it involves IgE antibodies, it’s considered an allergy. All other immune responses are considered hypersensitivities.
Yes, getting a rash from poison ivy is an allergic reaction.
The medical definition of an allergic reaction is a damaging immune response to an allergen.
Most people don’t have an allergic reaction response to their first exposure of urushiol (the allergen in poison ivy.) However, after being in exposed once, the body prepares an immune response and the next exposure causes the rash as the body tries to fight off the perceived threat of the allergen.
A good example of what is or isn’t an allergy is capsaicin the thing that makes chili peppers spicy. Capsaicin is a neurotoxin that binds to nerves triggering a pain sensation. That is not an allergy.
However there are people who are actually allergic to capsaicin. That means their immune response is triggered by capsaicin and the immune response causes inflammation and sometimes even difficulty breathing. For those people, the substance itself is both causing pain and the immune response is causing additional problems.
But most people don’t have a capsaicin allergy but capsaicin still causes pain even without the allergy.
It doesn’t matter how many other individuals have the reaction. What matters is the reaction itself. An allergic reaction is your immune system attacking something that is *actually harmless*.
The chemical in poison ivy that causes the rash is not in itself harmful. Your body could just let it hang out. The rash is purely an overreaction of your immune system, which has decided that this was a chemical that should be attacked. It takes at least one prior exposure for your immune system to build up this allergy, and it can take multiple exposures (so that sometimes people think they are not sensitive to poison ivy because it has never given them a reaction, but then later in life they suddenly do get a rash after contact with it). .
Same with pollen. Pollen is not at all harmful in and of itself. But in some people, the immune system decides that it is the enemy.
So the key question for defining an allergy is: would this thing cause any harm if the immune system didn’t attack it? If the answer is *no*, then it is an allergy. (There can be some shades of gray. Like, some substances might be (inherently) mildly irritating to your body, but not actually dangerous. If the immune reaction to one of these is worse than the intrinsic irritation, then you can still call it an allergy. If the intrinsic irritation is worse than the immune reaction, then the immune reaction is appropriate as it reduces harm, and therefore it is not an allergy. Also, another part of the true definition of an allergy is which parts of the immune system actually get activated – e.g. which types of antibodies are produced.)
An allergy is an overreaction of the body’s immune system to a foreign substance, called an allergen, that is typically harmless to most people. Think of it like the immune system thinking the allergen is a dangerous invader and launching an attack to try to get rid of it, even though it’s not actually harmful.
Allergies can be specific to certain things or substances, and some people may be more prone to allergies than others due to genetic factors. Different species can also have different tolerances for certain substances, so just because something is harmless to one animal or plant doesn’t mean it will be harmless to another. For example, dogs and cats can have allergies too, but they may be allergic to different things than humans.
If someone gets itchy after touching poison ivy, that would be considered an allergic reaction. In some cases, people may not have an allergic reaction but simply be more sensitive to a substance due to irritation. In that case, it wouldn’t be considered an allergy.
There isn’t really a hard and fast rule for what constitutes an allergy, as it can vary depending on the substance and the individual’s reaction. But allergies are generally considered to be fairly common, with anywhere from 10-30% of the population experiencing some form of allergy at some point in their lives.
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