The appearance of the rash is probably the least helpful clue, because it may be very different from one person to another. Scratch marks are often seen, along with scaly dry skin. The skin may become infected and show yellow crusts or little, pinpoint, pus-containing bumps. The skin also may get very thickened from long-term scratching and rubbing. If other family members or relatives have AD, asthma or hay fever, the diagnosis of AD is more likely.
AD is a familial disease, though the exact way it passes from parents to children is unclear.
If both parents are atopic, chances are even greater that their child will have it. AD is not contagious. AD inflammation results from too many reactive inflammatory cells in the skin. Research is seeking the reason why these cells over-react. When something triggers them, they don't turn off as they should.