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.
The most common type of eczema is atopic dermatitis, a chronic and inflammatory condition. Its cause is still unknown, but it occurs when the immune system goes into overdrive. The other common types are contact dermatitis, dyshidrotic eczema, hand eczema, neurodermatitis, nummular eczema, seborrheic eczema and xerotic eczema.
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).
Eczema usually appears between 6 months and 5 years of age. Infants typically develop it on their face, often affecting the cheeks and chin. However, it can appear on any part of the body. In most cases, the symptoms go away as a child grows older, but some children will continue to suffer from it into adulthood. It is also possible for adults to develop this condition suddenly.