[katieHaylor (OP)]

Daria says:

What causes us to suddenly become allergic to certain things after already having been exposed to them with no reaction for years or even decades? (To clarify the question - my personal example is that I became allergic to dust, certain plants, wool, cats and dogs, at the age of 8. Why not earlier? And why not forever? Almost all my allergies and violent reactions to allergens lasted for about 15 years, and I know other people that "grew-out" of allergies or got some later in their life.)

What do you think?

[evan_au]

The immune system is complicated!
It's not entirely clear why "Western" societies have an epidemic of allergies that are not seen in "traditional" societies.
Or what suddenly sensitises people to something in their environment.
...although "growing out of it" is fairly common - after a while, the immune system no longer considers the allergen a threat.

See: https://en.wikipedia.org/wiki/Hygiene_hypothesis

[PmbPhy]

Can we suddenly become allergic to things?

Daria says:

What causes us to suddenly become allergic to certain things after already having been exposed to them with no reaction for years or even decades? (To clarify the question - my personal example is that I became allergic to dust, certain plants, wool, cats and dogs, at the age of 8. Why not earlier? And why not forever? Almost all my allergies and violent reactions to allergens lasted for about 15 years, and I know other people that "grew-out" of allergies or got some later in their life.)

What do you think?

I'm confused. The subject line reads Can we suddenly become allergic to things? but your post indicates that you already know the answer to that question.

I know that we can become allergic to things. I also know that allergies can disappear as well. When I was a kid I had many cats. However in my mid 20s I was allergic to them big time. Then in my 40s the allergy was less. Now I have 3 cats and have no allergic reaction to them at all.

[chiralSPO]

Hi PmbPhy, and katieHaylor, I have taken the liberty of modifying the subject line of this thread to clear up any possible confusion. As PmbPhy noticed, the subject question did not quite match the question that Daria posed (no offense katie, I think you're doing a great job). I hope this does not interfere with the discussion.

As far as the topic goes... Yes allergies are very odd. I have heard that excessive sterilization in some homes and communities in "western" countries has been tied to an uptick in allergies. The explanations I have heard are that without constant exposure to pathogens the body's immune system either just chooses a new enemy (hmmm, we haven't destroyed any staph aureus recently, let's go nuts and destroy some shellfish proteins!!!) or loses the ability distinguish between "good" and "bad."

This is well beyond my expertise, but I will also point out that there are many chemicals that are known as "sensitizers." Most people, when first exposed to these compounds have no reaction at all, but after repeated exposures the body become "sensitized" and can have sever inflammatory or allergy-like responses. Urushiols, the active components of poison ivy is one such compound (these are also found in poison oak, poison sumac, and parts of the mango tree and cashew tree). I am lucky enough to have avoided sensitization to poison ivy thus far in my life (I only know of one instance when I knowingly came into contact with poison ivy, and with no ill effect) but I still avoid it like the dickens because I know that it could become an issue at any time.