[Harry01 (OP)]

I seem to have developed a contact allergy to some ingredient(s) from toothpaste from chronic overexposure. I am trying to find a toothpaste I am not allergic too as I constantly get this delayed reaction that wakes me up.

[paul cotter]

When an allergy occurs the immune system identifies a relatively innocuous substance as a major threat and it throws all it has at this misidentified hazard. Why this happens is not fully understood but a lot of current thinking suggests it may arise due to lack proper "exercise" for the immune system in one's early years, the so called hygiene hypothesis. It is thought that too clean an environment when developing leads to immune dysregulation. This is not proved as of yet.

[Harry01 (OP)]

Hmmm, sounds like a dubious theory. What about "sensitisation"? I find it astonishing how people confidently assert things when they simply don't know. It's like in their heads they imagine that the universe is simple. Hahahaha

[paul cotter]

I am not asserting anything, instead I offered one of the leading theories on the subject and I did add that it is not certain.

[vhfpmr]

I made myself allergic to deodorants simply by using it on broken skin. Having squeezed an acne spot, I sprayed my armpits as usual without a thought for the warning on the can not to use on broken skin, and that's all it took. I now develop an itchy red rash if I use the stuff.

For quite a few years after that I was able to use solid stick deodorants instead of aerosols, but one day a sharpish edge on the applicator casing scratched my armpit and that caused me to become allergic to the solid stick as well. I didn't bother washing the deodorant off immediately after the scratch because it didn't break the skin or draw blood, but it was still enough nevertheless.

I think these kind of allergies arise just because we're exposing ourselves to novel chemicals that evolution never had any experience of.

[Harry01 (OP)]

This is interesting. Thanks for sharing. Were you able to pin down the offending ingredient?

[Harry01 (OP)]

@paul cotter Understood. Yeah, I was having a go at them.