Can I apply Cetaphil to my son's groin?

Hello, my 3 year old boy scratches his penis and testicles. He has a very sensitive skin that itches easily (eczema), I have been creaming him morning and night with Cetaphil all over his body for months. However, it has been 2 weeks that he seems irritated (red skin) at the penis/testicle and it itches (the more he scratches the more it stings). Also, he is potty training so it doesn't help when he is wet.