Hi and welcome to HCM.
I havent heard such side effects of protein powder. YOu should find cause in something else. SOmetiems it is caused by hormonal
imbalance so he should check thyroid
hormones first. Secondly, it can be some dermatologic disorder,alergic or contact dermatitis
. Rarely osme infectious diseases have such effect. ANd third, you should be sure that he doesnt take steroids
, in this case you can consider side effects, WIsh you good health.