how do you cure a rash behind your armpit

IT could be your deodarant. Too many perfumes or scents. Did you know that men’s and women’s deodarants are different? Try the other sexes deodarant. Keep the area dry with powder and or baking soda. I myself am allergic to certain kinds. I switch between Dove and Degree for men. It sux using men’s but if it works then…hey whatever. Kellie