Eczema (from Greek έκζεμα) is a form of dermatitis, or inflammation of the epidermis. The term eczema is broadly applied to a range of persistent skin conditions. These include dryness and recurring skin rashes which are characterized by one or more of these symptoms: redness, skin edema (swelling), itching and dryness, crusting, flaking, blistering, cracking, oozing, or bleeding. Areas of temporary skin discoloration may appear and are sometimes due to healed lesions, although scarring is rare. In contrast to psoriasis, eczema is often likely to be found on the flexor aspect of joints.

Types

The term eczema refers to a set of clinical characteristics. Classification of the underlying diseases has been haphazard and unsystematic, with many synonyms used to describe the same condition. A type of eczema may be described by location (e.g. hand eczema), by specific appearance (eczema craquele or discoid), or by possible cause (varicose eczema). Further adding to the confusion, many sources use the term eczema and the term for the most common type of eczema (atopic eczema) interchangeably.

The European Academy of Allergology and Clinical Immunology (EAACI) published a position paper in 2001 which simplifies the nomenclature of allergy-related diseases including atopic and allergic contact eczemas. Non-allergic eczemas are not affected by this proposal.

The classification below is ordered by incidence frequency.

Types of common eczemas

• Atopic eczema (aka infantile e., flexural e., atopic dermatitis) is believed to have a hereditary component, and often runs in families whose members also have hay fever and asthma. Itchy rash is particularly noticeable on head and scalp, neck, inside of elbows, behind knees, and buttocks. Experts are urging doctors to be more vigilant in weeding out cases that are, in actuality, irritant contact dermatitis. It is very common in developed countries, and rising. (L20)
• Contact dermatitis is of two types: allergic (resulting from a delayed reaction to some allergen, such as poison ivy or nickel), and irritant (resulting from direct reaction to a solvent, such as sodium lauryl sulfate, for example). Some substances act both as allergen and irritant (wet cement, for example). Other substances cause a problem after sunlight exposure, bringing on phototoxic dermatitis. About three quarters of cases of contact eczema are of the irritant type, which is the most common occupational skin disease. Contact eczema is curable provided the offending substance can be avoided, and its traces removed from one's environment. (L23; L24; L56.1; L56.0)
• Xerotic eczema (aka asteatotic e., e. craquele or craquelatum, winter itch, pruritus hiemalis) is dry skin that becomes so serious it turns into eczema. It worsens in dry winter weather, and limbs and trunk are most often affected. The itchy, tender skin resembles a dry, cracked, river bed. This disorder is very common among the older population. Ichthyosis is a related disorder. (L85.3; L85.0)
• Seborrhoeic dermatitis (aka cradle cap in infants, dandruff) causes dry or greasy scaling of the scalp and eyebrows. Scaly pimples and red patches sometimes appear in various adjacent places. In newborns it causes a thick, yellow crusty scalp rash called cradle cap which seems related to lack of biotin, and is often curable. (L21; L21.0)