Atopic dermatitis (eczema). Usually beginning in infancy, this red, itchy rash most commonly occurs where the skin flexes — inside the elbows, behind the knees and the front of the neck. When scratched, the rash can leak fluid and crust over. People with atopic dermatitis may experience improvement and then flare-ups.
Contact dermatitis. This rash occurs on areas of the body that have come into contact with substances that either irritate the skin or cause an allergic reaction, such as poison ivy, soap and essential oils. The red rash may burn, sting or itch. Blisters may develop.
Seborrheic dermatitis. This condition causes scaly patches, red skin and stubborn dandruff. It usually affects oily areas of the body, such as the face, upper chest and back. It can be a long-term condition with periods of remission and flare-ups. In infants, this disorder is known as cradle cap.