The terms "dermatitis" and "eczema" are often used interchangeably. Eczema a superficial disease of the skin. It is of an inflammatory nature, associated with itching or even pain; and embraces about one-half of all cases of skin disease. It can be "acute" or "chronic" or both. Acute eczema refers to a rapidly evolving red rash which may be blistered and swollen. Chronic dermatitis refers to a longstanding irritable area. It is often darker than the surrounding skin, thickened and much scratched. It is often more generally called 'dermatitis'. Eczema can also be due to other naturally occurring environmental factors: cold or hot weather, and exposure to the sun. It results from a variety of different causes and has various patterns.
Different types of eczema are labeled atopic, nummular, dyshidrotic, seborrheic and xerotic.
Dermatitis affects about one in every five people at some time in their lives. Dermatitis venenata is caused by contact with the plant poison sumac, one of a range of plants in the Rhus genus which cause itching and rashes (including poison ivy R toxicodendron and poison oak R diversiloba).