Dermatitis, also known as eczema, is a group of diseases that results in inflammation of the skin. These diseases are characterized by itchiness, red skin and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved can vary from small to the entire body.Dermatitis is a group of skin conditions that includes atopic dermatitis, allergic contact dermatitis, irritant contact dermatitis and stasis dermatitis. The exact cause of dermatitis is often unclear. Cases may involve a combination of irritation, allergy and poor venous return. The type of dermatitis is generally determined by the person's history and the location of the rash. For example, irritant dermatitis often occurs on the hands of people who frequently get them wet. Allergic contact dermatitis occurs upon exposure to an allergen, causing a hypersensitivity reaction in the skin.Treatment of atopic dermatitis is typically with moisturizers and steroid creams. The steroid creams should generally be of mid- to high strength and used for less than two weeks at a time as side effects can occur. Antibiotics may be required if there are signs of skin infection. Contact dermatitis is typically treated by avoiding the allergen or irritant. Antihistamines may help with sleep and to decrease nighttime scratching.Dermatitis was estimated to affect 245 million people globally in 2015. Atopic dermatitis is the most common type and generally starts in childhood. In the United States, it affects about 10–30% of people. Contact dermatitis is twice as common in females than males. Allergic contact dermatitis affects about 7% of people at some point in time. Irritant contact dermatitis is common, especially among people who do certain jobs; exact rates are unclear.