Irritants can cause inflammation and itching, bringing on eczema. Harsh chemicals can cause a rash in anyone, but people with eczema may be sensitive to mild irritants, such as wool and synthetic fabrics, detergents, soaps, perfumes, and cosmetics. Stress or anxiety can cause a flare-up, too. So can sweating, along with wetting and drying your skin a lot, such as when you wash your hands. Cold, dry environments can also cause a flare.