It hurts under my armpit. . .?

My cousin had that happen, and it turned out her skin wasn't getting along with the type of deoderant she had. Gas has nothing to do with this. Buy a new brand of deoderant, try it out, and if it doesnt get any better, then you should tell your mom or dad, or anyone around you. Or go to a doctor. But i find it weird to go to the doctors if your armpit hurts. Hope i helped!