Both arm pits are kinda itching. no rash or bumps, but the big creases in skin is red and look irritated. why would just the creases be irritated?

Friction will do this. Sometimes enough moisture is present that a yeast infection occurs producing itching. Sometimes it's a reaction to deodorants, if you use them, or allergy/ irritation from tight clothing. For redness & itching, I prescribe a combination of an antiyeast & corticosteroid ointment which is a prescription medication. Discuss with your MD or ask your pharmacist to recommend combo