Most skin cells grow and shed every 28 to 30 days. If your baby has psoriasis, the skin cells in the affected area are maturing every three to four days instead. Those raised, scaly lesions are actually a buildup of skin. The redness is from extra blood being pumped to the area.
Nobody knows why the body decides to generate skin cells so rapidly, but the change is thought to be triggered by the immune system. There's a genetic factor, too — about a third of those with psoriasis have at least one family member with the condition. A child can develop psoriasis without a family history, though.
Childhood bouts of guttate psoriasis are sometimes triggered by an illness, like a cold or tonsillitis. Skin injuries — from scratching or rubbing, for example — and stress may make matters worse. (You may want to put little mittens or socks on your baby's hands if you see that he's scratching, especially during sleep.)