Small bumps spreading on body? doctor says its heat rash or allergies? it's been 6 days. very itchy. wrong diagnosis?

Check in again: TIme to let your doctor know that the problem is 1. not going away and 2. getting worse/spreading/bigger.

See dermatologist : Your best advice is to see a dermatologist to see what the rash is.

Allergies or hives: You need re-evaluation by your doctor or dermatologist. Hives (urticaria) is a form of allergic reaction with welts that come and go (increased on skin folds/creases, or after scratching). Many other causes of itchy rash - such as scabies (intense itching, starts in one place and spreads, small bumps + scratch marks, it spreads to others), drug reaction, food allergy, liver disease,... etc