The other measures you can take to help itch are to apply an OTC lotion like Sarna, as needed for itch, and to take an antihistamine like
BenadrylBenadryl
Benadryl allergy decongestant
Benadryl allergy sinus headache
Benadryl cold 25 mg or chlortrimeton 4 mg (both also OTC.) Antibacterial shampoos arent necessary. In egeneral, I agree with your dermatologist about folliculitis. If your symptoms persist for more than another 2-3 weeks, I'd get back to him, though.
Best.
Dr. Rockoff