Dermatitis
What is dermatitis?
Dermatitis refers to a group of itchy inflammatory conditions characterised by epidermal changes.
Dermatitis can be classified in a variety of ways. It may be classified by:
- Cause eg, allergic contact dermatitis, photosensitive dermatitis
- Clinical appearance eg, discoid dermatitis, hyperkeratotic dermatitis, and pompholyx
- Site of predilection eg, hand dermatitis, eyelid dermatitis, or lower leg dermatitis.
In many cases, various factors may all act as underlying triggers together (allergic, irritant, and endogenous factors, especially in hand dermatitis).
The terms dermatitis and eczema are often used interchangeably. All eczema is a dermatitis, but not all dermatitis is eczema.
- Dermatitis, strictly speaking, includes any cause of skin inflammation affecting the epidermis.
- Eczema is derived from the Greek word for “to boil or bubble over”, which pathologically manifests as oedema within the epidermis (called spongiosis).
The term dermatitis is sometimes mistakenly attributed to mean an eczema induced by an occupational factor; this is erroneous.
Who gets dermatitis?
Dermatitis is common, affecting about one in every five persons at some stage in their life.
Different types of dermatitis are more frequent at different stages of life, for example:
- Atopic dermatitis and pityriasis alba are more common in children
- Hand eczema is more common in young and middle-aged adults
- Venous or gravitational eczema, asteatotic dermatitis, and nummular eczema are more common in middle and older age groups.
There are no consistent racial factors influencing disease frequency.
What are the clinical features of dermatitis?
Dermatitis may be either acute or chronic, and although the mechanism by which the dermatitis develops may be the same, the appearances may be starkly different.
- Acute dermatitis will show redness or swelling, papulation, vesiculation, oozing and weeping, and even blistering.
- Chronic eczema will show skin thickening with accentuation of the skin creases, hyperkeratosis, scaling, fissuring, excoriation, and hyperpigmentation.
- Subacute dermatitis will show features of both.
What are the types of dermatitis?
Exogenous dermatitis is the result of an external factor or insult that induces skin inflammation. Common causes include:
- Allergic contact dermatitis — due to immune sensitisation of an individual to an allergen, often at even low concentration, such as nickel, hair dye, rubber, or perfumes; identified by patch testing.
- Irritant contact dermatitis — will occur in anyone exposed to an irritant at sufficient concentration for long enough; irritants include soaps, detergents, organic solvents, degreasing agents, abrasives, desiccants, dust, urine, and even water
- Photosensitive dermatitis — triggered by light or UV radiation
- Post-traumatic dermatitis — due to physical injuries such as abrasions, burns, or surgery (eg, autonomic denervation dermatitis)
- Dermatitis induced by local skin infections such as bacterial, fungal, and viral e.g. molluscum contagiosum and HTLV-1 disease
- Drug-induced dermatitis.
Endogenous dermatitis occurs because of often ill-understood internal factors. Common types include:
- Atopic dermatitis — a common form of dermatitis occurring in children and adults, and often occurring in families with a background of asthma and hay fever
- Seborrhoeic dermatitis — common chronic eczema affecting the face, scalp, ears and major flexures, due to a reaction to yeasts that colonise the skin
- Discoid (nummular) dermatitis — coin-shaped patches of dermatitis usually affecting the limbs
- Lichen simplex — chronic dermatitis that thickens due to perpetual scratching
- Pityriasis alba — pale patches of dermatitis affecting the cheeks
- Hand dermatitis — internal, external irritants and allergic factors may all play a part even in a single individual
- Eyelid dermatitis — again, often of mixed cause
- Otitis externa — dermatitis affecting the ear canal and the pinna
- Venous or gravitational dermatitis — dermatitis due to malfunction of the lower leg vein valves
- Juvenile plantar dermatitis — a glazed and fissured forefoot eczema occurring in children
- Metabolic dermatitis — seen in some nutritional and endocrine disorders
- Chronic superficial scaly dermatitis — finger-shaped patches of eczema occurring on the trunk
- Asteatotic dermatitis — crazy-paving shaped dermatitis due to degreasing of the skin from excessive bathing and soap use on the legs in the elderly
- Halo dermatitis or Meyerson naevus — this can surround a benign mole
- Erythrodermic dermatitis — severe dermatitis when more than 80% of the skin is affected.
How is dermatitis treated?
- Topical therapies (emollients, potassium permanganate soaks, paste bandages, topical steroids, topical anti-inflammatory agents)
- Physical therapies (Ultraviolet B and Psoralens UVA (PUVA))
- Systemic Agents (Antihistamines, antibiotics & antivirals, immunosuppressive therapies, biological therapies, oral small molecules)