Small red bumps some have a white head on them. started on upper chest and now on arms. what could this be?

Doctor can evaluate: Bumps may be conditions such as keratosis pilaris, eczema, comedones, or folliculitis. Each would have a different treatment, so a primary care doctor or a dermatologist can evaluate and give some recommendations. Rashes are hard to describe in words. Little white heads are more likely folliculitis. If recently using a hot tub, such a rash could be due to that.