What Causes Itching Under Arms And Around Upper Thighs?

I became having extreme ithing under my arms, around my upper thighs and waist. No rash. However immediatly after I scratched these areas I developed large white welts surrounded by redness. The more I scratched the more wets appeared. No tongue involment but throated became swollen. After taking Benadyl the itching stopped and the large wells disseminated into smaller patches of red rash.