Re: Armpit rash
Have you recently changed the antiperspirant/deodorant that you use? You could be sensetive to that.
I would stop using soap/shower gel to wash the area, and instead wash it with plain Aqueous Cream, a very mild clesner.
Dont put any deodorant on the armpit, that will probably increase the irritation.
Put some 1% Hydrocortisone on in three times a day, that should help in a few days.