I have itchy white lumps appearing on my thigh & lower back. what could they be?

Folliculitis? Heat?: Folliculitis is tiny pustules where the hair follicles are. Heat rash is related to sweating a lot, with or without "blocked" sweat glands or oil glands. Other times it's related to sports equipment friction, bacteria, moisture, etc... Being in a hot tub can lead to a "hot tub" rashes. Rashes are quite difficult to describe in words, so a doctor needs to look at the rash to make a diagnosis.

Unsure: These lesions would likely need to be examined and more history obtained to be able to provide you with useful input about the diagnosis or possible treatment.