The terms "dermatitis" and "eczema" are often used interchangeably. Eczema a superficial inflammatory disease of the skin which causes it to become red, itchy and scaly; it accounts for 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 and often 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.
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).