A variety of skin conditions marked by red and scaly or crusted skin are referred to as dermatitis and sometimes as eczema. These include atopic dermatitis, which tends to develop in front of the elbows and behind the knees, contact dermatitis, and seborrheic dermatitis, which is characterized by scaling of the skin around the nose, ears, eyebrows, and scalp. Characterized by sharply demarcated areas of red and scaly skin, psoriasis affects more than 3 million Americans. Lesions typically appear on the scalp, elbows, knees, legs, and nails, but may affect other parts of the body. Infections and infestations.
Viral infections can produce warts or small growths called molluscum contagiosum.
Cold sores on the lips, caused by a herpesvirus, and shingles, caused by the same virus as chicken pox, are other examples of viral skin conditions. Bacterial infections of the skin include impetigo, which tends to affect children, and folliculitis, which starts in hair follicles. The skin may also be infected by fungi, as in athlete's foot and ringworm, and infested by lice, mites, and other parasites. Hair and nail disorders. Hair shafts may become abnormal, and follicles may shrink or become deformed.