Dermatitis is a term used for different types of skin inflammation, typically characterized by itchiness, redness and a rash.

[1] Allergic contact dermatitis occurs upon exposure to an allergen, causing a hypersensitivity reaction in the skin.

[1] Prevention of atopic dermatitis is typically with essential fatty acids,[4] and may be treated with moisturizers and steroid creams.

[5] 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.

Also, the area of the skin on which the symptoms appear tends to be different with every type of dermatitis, whether on the neck, wrist, forearm, thigh or ankle.

[19] Typical affected skin areas include the folds of the arms, the back of the knees, wrists, face and hands.

[24] Other major health risks for people with dermatitis are viral and bacterial infections because atopic dermatitis patients have deficiencies in their proteins and lipids that have barrier functions along with defects in dendritic cells and as a result are unable to keep foreign invaders out, leading to recurring infections.

[25] If left untreated, these infections may be life-threatening, so skin barrier improvement (such as daily moisturizing to minimize transepidermal water loss) and anti-inflammatory therapy are recommended as preventative measures.

The hygiene hypothesis postulates that the cause of asthma, eczema, and other allergic diseases is an unusually clean environment in childhood which leads to an insufficient human microbiota.

Further adding to the confusion, many sources use the term eczema interchangeably for the most common type: atopic dermatitis.

[27] 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.

Itchy rash is particularly noticeable on the head and scalp, neck, inside of elbows, behind knees, and buttocks.

About three-quarters of cases of contact eczema are of the irritant type, which is the most common occupational skin disease.

In newborns, it causes a thick, yellow, crusty scalp rash called cradle cap, which seems related to lack of biotin and is often curable.

(ICD-10 L21; L21.0) There is a connection between seborrheic dermatitis and Malassezia fungus, and antifungals such as anti-dandruff shampoo can be helpful in treating it.

[44] Dyshidrosis (dyshidrotic eczema, pompholyx, vesicular palmoplantar dermatitis) only occurs on palms, soles, and sides of fingers and toes.

Tiny opaque bumps called vesicles, thickening, and cracks are accompanied by itching, which gets worse at night.

(ICD-10 I83.1) Dermatitis herpetiformis (Duhring's disease) causes an intensely itchy and typically symmetrical rash on arms, thighs, knees, and back.

[48] In fact, it may increase the risk of skin infection and of unwanted effects such as allergic reaction to certain moisturizers and a stinging sensation.

[49] Oils with fatty acids that have been studied to prevent dermatitis include:[51][52] In the 1950s Arild Hansen showed that infants fed skimmed milk developed essential fatty acid deficiency which was characterized by an increased food intake, poor growth, and a scaly dermatitis, and was cured by the administration of corn oil.

There is no known cure for some types of dermatitis, with treatment aiming to control symptoms by reducing inflammation and relieving itching.

[54] The American Academy of Dermatology suggests using a controlled amount of bleach diluted in a bath to help with atopic dermatitis.

[56] House dust mite reduction and avoidance measures have been studied in low quality trials and have not shown evidence of improving eczema.

[57] Low-quality evidence indicates that moisturizing agents (emollients) may reduce eczema severity and lead to fewer flares.

[65] Of the second generation antihistamines studied, fexofenadine is the only one to show evidence of improvement in itching with minimal side effects.

[44] In September 2021, ruxolitinib cream (Opzelura) was approved by the U.S. Food and Drug Administration (FDA) for the topical treatment of mild to moderate atopic dermatitis.

[89] Dermatitis is most commonly seen in infancy, with female predominance of eczema presentations occurring during the reproductive period of 15–49 years.

[93] from Ancient Greek ἔκζεμα ékzema,[94] from ἐκζέ-ειν ekzé-ein, from ἐκ ek 'out' + ζέ-ειν zé-ein 'to boil' The term atopic dermatitis was coined in 1933 by Wise and Sulzberger.

[97] In 2019, the European Union released a document about claims made concerning cosmetics,[99] but this was issued as guidance, not a regulation.

[100] Monoclonal antibodies are under preliminary research to determine their potential as treatments for atopic dermatitis, with only dupilumab showing evidence of efficacy, as of 2018.