Dermatitis
Definition
Contact dermatitis is an inflammatory response of the skin to an allergen (contact allergic dermatitis) or irritant (irritant contact or primary irritant dermatitis). Contact dermatitis can cause discomfort and embarrassment and is the most common skin condition among workers' compensation claims.
The main pathological feature of contact dermatitis is intercellular oedema of the epidermis, which may result in intraepidermal vesicle and bullae formation in acute cases; and papules, scaling, and lichenification in chronic cases. Within the dermal layer, various cells congregate around the dilated capillaries to aid in the inflammatory response.
Primary irritant dermatitis results from direct injury to the skin. It affects individuals exposed to specific irritants and generally produces discomfort immediately following exposure. Contact allergic dermatitis is an allergic reaction, usually to a protein, in a substance contacting the skin, to which there has been prior sensitisation. The occurrence of a reaction due to the interaction of either of these mechanisms and sun exposure is known as photodermatitis (photoallergic or photoirritant contact dermatitis)
Aetiology / Risk Factors
- Fair skinned people have higher incidence
More common in females
Common in infants—nappy rash
Prolonged and repeated exposure to chemicals, soaps, cleaning agents, strong alkalis
Photosensitivity can lead to dermatitis in sun-exposed areas
Contact with plants or other substances including nickel sulphate (various metal alloys), potassium dichromate (cements, household cleaners), formaldehyde, ethylenediamine (dyes, medications), mercaptobenzothiazole (rubbers), thiram (fungicides), and paraphenylenediamine (dyes, photographic chemicals).
Symptoms & Signs
- Acute contact dermatitis presents as clear fluid-filled vesicles or bullae that appear on bright red oedematous skin. As the lesions break, skin becomes exudative and weeps clear fluid.
- Subacute contact dermatitis is characterised by less oedema and formation of erythema and papules.
- Chronic contact dermatitis presents with minimal oedema. Scaling, skin fissuring, and lichenification may be noted.
- Contact urticaria has a wheal and flare response at the site of exposure.