Contact dermatitis

Specialties > Dermatology

Background knowledge 🧠

Definition

Contact dermatitis is an inflammatory skin condition caused by direct contact with an irritant or allergen.
It is classified into irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD).
Commonly presents as erythema, scaling, and pruritus at the site of contact.

Epidemiology

ICD is the most common form, accounting for 80% of all cases of contact dermatitis.
ACD affects approximately 10% of the population in the UK.
More common in females, possibly due to exposure to allergens in cosmetics and household products.
Occupational dermatitis is a significant concern in healthcare workers, hairdressers, and construction workers.

Aetiology and pathophysiology

ICD: Caused by direct chemical or physical damage to the skin (e.g., acids, alkalis, solvents).
ACD: A delayed hypersensitivity reaction, involving sensitisation to an allergen and subsequent re-exposure.
Common allergens include nickel, rubber, fragrances, and preservatives.
Chronic exposure can lead to skin barrier disruption and persistent inflammation.
Genetic predisposition may play a role, particularly in ACD.

Types

Irritant Contact Dermatitis (ICD): Caused by direct damage to the skin’s outer layer.
Allergic Contact Dermatitis (ACD): Immune-mediated response to a specific allergen.
Phototoxic Dermatitis: Caused by a combination of irritants or allergens and exposure to UV light.
Occupational Dermatitis: Resulting from exposure to irritants or allergens in the workplace.
Contact Urticaria: Immediate reaction to contact with an allergen, typically involving histamine release.

Clinical Features 🌡️

Symptoms

Pruritus: Most common symptom, can be severe and distressing.
Burning or stinging sensation, particularly in ICD.
Pain: More common in acute, severe cases.
Dry, cracked skin in chronic cases.
Blistering or weeping lesions in severe cases, particularly ACD.

Signs

Erythema: Redness of the affected area.
Oedema: Swelling, especially in acute cases.
Vesicles: Small fluid-filled blisters, typically seen in ACD.
Lichenification: Thickened, leathery skin in chronic cases.
Excoriations: Scratch marks due to intense itching.
Crusting and scaling: Often seen in the later stages.

Investigations 🧪

Tests

Patch Testing: Gold standard for diagnosing ACD; involves applying allergens to the skin to identify specific triggers.
Skin Prick Testing: Sometimes used, but less common in diagnosing contact dermatitis.
Skin Biopsy: Rarely required but can be useful in unclear cases to rule out other dermatological conditions.
Blood Tests: Not routinely used, except to exclude differential diagnoses like infections.
History and Clinical Examination: Essential to identify potential irritants or allergens based on patient exposure.

Management 🥼

Management

Avoidance of known irritants or allergens: Key to preventing further episodes.
Topical corticosteroids: Mainstay of treatment for reducing inflammation; potency depends on severity.
Emollients: Regular use to restore the skin barrier and prevent further damage.
Antihistamines: For symptomatic relief of itching.
Referral to dermatology: Considered in severe, chronic, or unclear cases.

Complications

Secondary bacterial infection: Due to skin barrier disruption and scratching.
Chronic lichenification: From prolonged scratching and inflammation.
Psychological impact: Can lead to anxiety, depression, and reduced quality of life.
Occupational implications: May require changes in job or duties if linked to workplace exposure.

Prognosis

Good prognosis if identified triggers are avoided and appropriate treatment is followed.
Chronic cases may persist or recur, especially with ongoing exposure to irritants/allergens.
Some cases may require long-term management strategies, including regular use of emollients and intermittent corticosteroids.

Key points

Identify and avoid triggers to prevent recurrence.
Use of topical corticosteroids and emollients is central to management.
Referral to dermatology may be necessary for severe or unclear cases.
Educate patients on the chronic nature of the condition and importance of adherence to treatment.

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