Dermatitis

Dermatitis is a blanket term meaning any "inflammation of the skin" (e.g. rashes, etc.). There are several different types of dermatitis. The different kinds usually have in common an allergic reaction to specific allergens. The term could be used to refer to eczema, which is may also be called dermatitis eczema or eczematous dermatitis. A diagnosis of eczema often implies childhood or atopic dermatitis, but without proper context, it means nothing more than a "rash".

Contact dermatitis

Contact dermatitis is skin inflammation resulting from contact with an allergen. Rashes from contact dermatitis are typically decently large in size, and in some cases could remain for weeks, although several days could be sufficient time for them to heal. Contact dermatitis could be acute, but it is also possible for chronic contact dermatitis to develop in an individual.

Babies, infants, and the elderly could be severely affected by contact dermatitis. Diaper dermatitis is a common form of irritant contact dermatitis in infants. In the elderly, topical medications are a common cause of allergic contact dermatitis.

Types:

Contact dermatitis could be classified as any of the following types:

Allergic contact dermatitis (ACD)
Contact urticaria
Irritant contact dermatitis (ICD)
Photodermatitis (photoallergic dermatitis and phototoxic dermatitis)

Causes and risk factors:

Contact dermatitis is caused by exposure to certain allergens. The following are some that could cause this condition:

Chemicals
Highly alkaline products
Nickel
Paraphenylenediamine
Poison ivy
Poison oak
Poison sumac
Potassium dichromate
Toxicodendron plants