The exact cause is not known, but AD results from a combination of family heredity and a variety of conditions in everyday life that trigger the red, itchy rash. Time of onset. This type of eczema usually begins during the first year of life and almost always within the first five years. It's seldom present at birth, but it often comes on after six weeks. Other rashes also can start at that time, so it may be confusing at first, but most rashes disappear within a few days to weeks.
AD tends to persist.
It may wax and wane, but it keeps coming back. Atopic dermatitis also is a very itchy rash. Much of the skin damage comes from scratching and rubbing that the child cannot control. In babies, the rash usually starts on the face or over elbows and knees, places that are easy to scratch and rub. It may spread to involve all areas of the body, although the moist diaper region is often protected.