Contact dermatitis may be caused by immune or nonimmune factors. In the first case we talk about allergic contact dermatitis, in the second - a simple contact dermatitis. Simple contact dermatitis occurs more frequently than allergic. Contact dermatitis is an inflammatory skin disease. Contact dermatitis can be caused phototoxic and photoallergic reactions when the skin lesion occurs under the action of a chemical substance, or an allergen and sunlight. Simple contact dermatitis is caused by chemicals that have an irritating effect (like acid and alkali). Allergic contact dermatitis develops as a delayed-type allergic reaction. Depending on the duration of the impact of contact dermatitis can be acute (edema and wetting) and chronic (itching and peeling). In developed countries 5-20% of the population suffers from contact dermatitis, with a simple contact dermatitis disseminated more widely than allergic. With a simple contact dermatitis lesions parts have clear borders and are often located in the areas with thin skin (eyelids, skin folds), or where the irritant is in contact with the skin under the bandage, clothing, gloves  and, certainly, under the hair. Rash may be different - from the red spots to express edema, vesicles and ulcers. Allergic contact dermatitis begins with exposure of the allergen, captures the surrounding skin and often extends to the remotest parts of the body. Rash is presented by erythemas, papules and vesicles, with a presence of a strong itch. In chronic cases peeling occurs. A classic example of allergic contact dermatitis - dermatitis caused by certain plants, in particular, Rhus toxicodendron, in which the rash often has a linear shape and located at open areas of the body. Treatment of simple contact dermatitis confined to elimination of irritating factor and wear protective clothing, gloves, etc. Allergic contact dermatitis shall be treated by an identification and removal of the allergen. If this does not help, designated ointments or creams with glucocorticoids are being prescibed, with either potent or maximum strength. When you defeat the hairy scalp rashes, as well as with common rashes you will need some glucocorticoids for ingestion. Identification of the allergen is a difficult task, sometimes requiring a considerable amount of time. An allergic nature of the disease is indicated by an unusual localization of rash and ineffective previous treatment. Normally the patient has to describe in detail about the substances he was dealing at work and at home, what exactly cosmetics and medicines are being used. The most common contact allergens - parabenzoic acid esters, nickel sulfate, potassium bichromate, neomitsin, formaldehydes, etc. There are application tests to help identify the allergen, however those are contraindicated with common rashes and while receiving glucocorticoid treatments.