Inflammation of the skin is called dermatitis or eczema depenthng upon the nature of the causative agent. If the inflammation is caused by exogenous factors, then convention is to call the condition a dermatitis, whereas inflammation produced by endogenous factors is called an eczema.An inflammatory response of the skin is probably initiated by changes to the local blood vessels which become more permeable and dilated as a consequence of the inflammation. Since the epidermis is nourished by diffusion of fluids from the capillaries of the dermis (Part 1), the increased volume of fluid leaving the dermal blood vessels enters the epidermis to cause swelling and a disruption of the skin's normal keratinising processes. This ultimately manifests as scaling and, if the fluid accumulation is severe, as blisters on the skin. The dilated vessels are responsible for a red coloration of the skin and the action of chemical mediators on the nerves produces itching. The histological term for this type of oedema of the epidermis is called spongiosis.
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