Eczema. Computer artwork of the epidermis (upper skin layer) of skin affected by eczema. Eczema is a skin inflammation characterised by an itchy pink rash on the skin's surface, often accompanied by small fluid-filled vesicles that weep and become crusted. Many factors can trigger the rash, but all tend to produce the same histological features. Fluid accumulates in the epidermis, resulting in separation of the cells (spongiosis). Clumps of epidermal cells disintegrate to form vesicles. Blood vessels in the underlying dermis are dilated, and an immune response (white blood cells, green) can be triggered.