Contact Dermatitis
Contact dermatitis is an inflammatory skin condition affecting the epidermis and dermis, caused by exposure to an external irritant or allergen. It is subclassified into irritant and allergic contact dermatitis.
This updated UKMLA guide to contact dermatitis is based on NICE CKS, which covers causes, symptoms, diagnosis, and management.
Causes and Risk Factors
There are 2 subtypes of contact dermatitis:
| Type | Description | Causes |
|---|---|---|
| Allergic contact dermatitis (~20%) | Type IV (delayed) hypersensitivity reaction that occurs after sensitisation and subsequent re-exposure to an allergen | Common allergens include:
The most common allergens is nickel. |
| Irritant contact dermatitis (~80%) | Non-immunological inflammatory reaction caused by direct physical or toxic effects or an irritating substance on the skin (no prior sensitisation is required) | Common irritants include:
Contact with nappy is the most common cause in infants |
Occupational contact dermatitis is common (~60% are irritant, ~53% are allergic):
- Most common: contact with soaps and cleaning products (e.g. cleaners) and working with wet hands
- Other occupations with high rates of occupational dermatitis
- Beauticians
- Cooks
- Florists
- Hairdressers and barbers
- Metalworking machine operatives
- Dental practitioners
Clinical Features
It is not easy to clinically distinguish between atopic dermatitis and contact dermatitis, and the underlying cause may be mixed.
Allergic Contact Dermatitis
The reaction typically develops 24-72 hours AFTER re-exposure to the allergen:
- Itching is the predominant symptom
- Increase in erythema
- Blistering, weeping, and/or oedema may develop in acute and severe cases
- Dermatitis may affect areas not directly in contact with the allergen (e.g. transfer of nail varnish from the fingers to the eyelids)
Resolution can take many days, with or without treatment.
Classic distribution patterns and associated allergens:
- Earlobes / neck = nickel jewellery
- Wrists = watches, bracelets
- Hands = gloves, occupational chemicals
- Face = cosmetics, nail varnish, skincare products
- Scalp = hair dye
- Periumbilical area = belt buckles, buttons containing nickel
- Feet = footwear materials
- Axillae = deodorants / fragrances
Irritant Contact Dermatitis
The timing depends on the strength and duration of irritant exposure:
- Exposure to strong irritants (e.g. strong acids or alkalis) can cause immediate reactions
- Mild irritants (e.g. water) usually require prolonged or repeated exposure before a reaction becomes apparent
Clinical features may include:
- Stinging, smarting, burning, dryness, tightness, and chapping
- Skin changes are usually restricted to the area of irritant contact
- Protected areas may be spared, e.g. skin protected by gloves
- Distribution can help identify the trigger, e.g. dermatitis in finger webs or under rings may suggest repeated exposure to water or detergents
Avoidance of the causative agent usually leads to resolution of symptoms within a few days.
Investigation and Diagnosis
Gold standard: skin patch testing
A careful and comprehensive clinical history checking for possible precipitating, aggravating and relieving factors is important, including:
- Contact with potential allergens or irritants
- Occupations (past and present) – check if symptoms improve at weekends and during holiday, and recur on return to work
- Household and recreational activities
- Hobbies
Skin patch testing is for contact dermatitis, and skin prick test is for IgE-mediated allergies.
Management
1st line:
- Avoid the stimulus if the causative agent has been identified (most important)
- 8-12 weeks of avoidance may be needed before clinical improvement
- If complete avoidance not possible: advise on measures to prevent or minimise contact with affected skin
- Use liberal emollients and soap substitutes to maintain skin hydration and improve barrier repair
Symptomatic treatment with topical corticosteroids may be used
Do not prescribe aqueous cream as it is thought to cause a disproportionate amount of skin reactions.
If contact dermatitis is confirmed to be associated with occupation:
- The employer is legally obliged to assess health risks at work and prevent (or if this is not reasonably practicable) adequately control exposure to hazards (for example by change of duties or suitable personal protective measures).
- The employer has a legal duty to report a case of the disease to the Health and Safety Executive (HSE)