Dermatitis and eczema are words that are often used interchangeably to describe a variety of distinct skin conditions in which there is epidermal and dermal inflammation and nearly always intense itching.
Acute dermatitis is characterised by erythema, vesiculation and oozing, often with oedema. Histologically, the hallmark of acute dermatitis is spongiosis (intraepidermal vesicles).
Subacute dermatitis is similar but with scaling and crusting. Chronic dermatitis results in thickened dry patches, and is often lichenified from chronic rubbing (increased skin markings). Lichenification is often predominantly follicular in pigmented skin.
Types of dermatitis:
Read more about atopic dermatitis on DermNet.
Students are expected to have in depth knowledge about atopic dermatitis because it affects up to 20% of the population and causes considerable distress and ill health. Its prevalence is greatest in childhood, generally starting in the first few months of life, becoming more severe in infancy and often improving in school years.
Diagnosis depends on clinical findings, which vary with the age and stage of the disease. The main features are:
Flare-ups may be precipitated by:
Atopic eczema is frequently complicated by infection with Staphylococcus aureus and sometimes Streptococcus pyogenes (impetiginised eczema) and less frequently by Herpes simplex (eczema herpeticum). Warts and molluscum contagiosum tend to be more prevalent and extensive.
The pathogenesis appears involve release of vasoactive substances from mast cells and basophils as an IgE-mediated hypersensitivity reaction. There is a TH2 pattern of cytokine release from T helper lymphocytes in the epidermis and dermis with low levels of TH1 lymphocytes and gamma interferon. It is not known why the incidence of atopic dermatitis appears to be increasing; theories include increased hygiene and decreased exposure to micro-organisms and greater exposure to house dust mite. Prick tests are often positive but are not useful in making the diagnosis.
Affected sites vary with age. Infantile eczema commonly affects the face, sparing around the mouth and later the hands, feet and elsewhere. In older children, eczema tends to affect flexures, particularly antecubital and popliteal fossae. Adults frequently develop irritant hand eczema. Bilateral nipple eczema is common. Erythrodermic eczema refers to involvement of the entire body and the patient may require hospitalisation for wet dressings and sedation.
Management of atopic eczema involves:
Read more about nummular or discoid dermatitis on DermNet.
Nummular or discoid dermatitis/eczema has two forms, resulting in acute exudative plaques or less inflamed dry patches for weeks to months. It may arise at any age. Clusters of round or oval plaques may be localised to lower legs or other sites or generalised. The initial lesion may be precipitated by trauma or infection.
Management of nummular dermatitis involves:
Read more about irritant contact dermatitis on DermNet.
Irritant contact dermatitis arises when the skin is exposed acutely or chronically to chemical or physical agents that damage the skin. Irritant hand dermatitis is very prevalent in certain occupations such as cleaning and hairdressing, especially in atopic subjects. Irritant reactions include:
Typical irritants include friction and abrasion, water, dry and/or cold air, detergents, solvents, acids and alkalis, oxidising and reducing agents, prickly plants and fibreglass, enzymes, dirt, urine (napkin dermatitis) and many other substances.
Irritant dermatitis occurs at the site of direct injury to the cells. Gradual onset of dermatitis arises from loss of the skin barrier and inadequate repair mechanisms. It can be confused with or coexist with allergic contact dermatitis.
Management of irritant contact dermatitis involves:
Read more about allergic contact dermatitis on DermNet.
Allergic contact dermatitis refers to cutaneous delayed hypersensitivity reactions and may be confirmed by patch testing. The dermatitis may be acute, subacute, chronic or relapsing and may coexist with another form of dermatitis.
The pattern of distribution may give a clue to the origin, but although it may initially be confined to sites of contact the dermatitis may spread or generalise. Very small amounts of the allergen may be sufficient to cause dermatitis in sensitised individuals.
Management of allergic contact dermatitis is similar to irritant contact dermatitis.
Dermatologists use epicutaneous patch tests to identify contact allergens but interpretation of the results requires considerable experience. The standard series of about 24 common contact allergens may be supplemented by numerous other known or suspected compounds in low concentration. The test substances are applied to small plastic or aluminium chambers on special non-allergic tape. The patches are applied to the upper back and removed after 48 hours. The skin is observed over at least the next 48 hours. Eczematous reactions suggest contact allergy but may also be irritant in nature (non-allergic), especially in atopic subjects, and detected allergy may not be relevant to the presenting complaint.
The most common contact allergens include nickel, cobalt and chrome, fragrances, various anti-oxidant compounds used in the manufacture of rubber, preservatives and adhesives.
Read more about lichen simplex on DermNet.
Lichen simplex chronicus is a localised form of dermatitis in which there is lichenification because of rubbing and scratching; the patches become increasingly itchy so it is difficult to stop scratching. Well-defined papules and bumpy thickened plaques are found most often in adults on the nape of the neck, occipital scalp, lower legs, forearms, vulva or scrotum.
Management of lichen simplex involves:
Read more about nodular prurigo on DermNet.
Nodular prurigo is an uncommon chronic skin disease in which there are crops of intensely itchy firm nodules, sometimes associated with atopic dermatitis. Severe nodular prurigo is very debilitating and difficult to treat effectively. Individual lesions may be distinguished from squamous cell carcinoma by biopsy. Prurigo mitis or papular prurigo is a similar condition with itchy papules.
Read more about pompholyx on DermNet.
Pompholyx, also known as dyshidrotic or vesicular palmar eczema, refers to acute, chronic or relapsing blistering of the fingers, palms and /or soles. Crops of irritable deep-seated vesicles are followed by scaling and fissuring of the affected areas and may be complicated by Staphylococcus aureus infection. Sweating in response to emotional stress or heat may precipitate vesicles in some individuals. Pompholyx sometimes presents as an id reaction to tinea pedis (‘one foot, two hands’ syndrome) or as an expression of contact dermatitis to nickel.
Management of pompholyx involves:
Read more about seborrhoeic dermatitis on DermNet.
Seborrhoeic dermatitis is a common chronic erythematous scaly dermatosis affecting the following sites:
Seborrhoeic dermatitis may affect infants, presenting within the first few months postpartum as cradle cap or napkin dermatitis and sometimes spreading widely. It is rare after the age of one year. Adult-type seborrhoeic dermatitis usually presents after the age of 20 but may occur any time after puberty.
Seborrhoeic dermatitis appears to be an inflammatory response to Malassezia yeasts, which proliferate in oily skin (seborrhoea). It sometimes progresses to psoriasis; unusually extensive seborrhoeic dermatitis is sometimes called “sebopsoriasis”. Seborrhoeic dermatitis is particularly troublesome in patients infected by human immunodeficiency virus and those with Parkinson’s disease.
Characteristically, the scale is yellowish and greasy or white and bran-like (pityriasiform) associated with variable nummular or annular pale pink to bright red patches. Itching tends to be absent or mild.
Management of seborrhoeic dermatitis involves:
Read more about asteatotic dermatitis on DermNet.
Asteatotic dermatitis is also known as eczema craquelé and xerotic eczema and is due to the skin drying out. It generally affects the lower legs resulting in pruritic dry cracked red patches.
Management of asteatotic dermatitis involves:
Read more about venous eczema on DermNet.
Venous eczema is also known as stasis or gravitational eczema and is a manifestation of chronic venous insufficiency following deep venous thrombosis. Varicose eczema is a variant associated with visible varicose veins. Venous eczema affects the lower legs. It may be unilateral or bilateral. There is a high risk of contact allergy so patch testing should be considered.
Management of venous eczema involves:
Read more about autosensitisation dermatitis on DermNet.
Autosensitisation dermatitis is the rash that appears on the trunk and limbs due to generalisation of a previously localised condition such as asteatotic or venous eczema. It may appear similar to nummular dermatitis and can be intensely pruritic, requiring systemic steroids for control. An id reaction is autosensitisation dermatitis arising in response to a fungal infection.