Eczema (top) and acne (bottom), illustration. The effect of the conditions on the skin's surface are shown at left. At right are cross-sections through the skin. Eczema is inflammation of the skin characterised by itchy pink scales. Some of the epidermal cells (pink cells, top right) have broken down to form large yellow vesicles containing inflammatory cells. These vesicles can rupture onto the skin's surface to form crusts. At bottom right a pustule (pus-filled blister, yellow) is forming in a pore in the skin. The poree has become blocked with sebum, an oily substance produced by sebaceous glands. This allows bacteria present to multiply, causing inflammation and a pimple or pustule.