Dermatologists serving Lehigh Valley. Rated 5/5 (1 reviews). From their website: Acne is the most frequent skin condition seen by medical professionals. It consists of pimples that appear on the face, back and chest. About 80% of adolescents have some form of acne and about 5% of adults experience acne. In normal skin, oil glands under the skin, known as sebaceous glands, produce an oily substance called sebum.\\