Contact Dermatitis

Contact dermatitis is a type of acute or chronic inflammation of the skin caused by exposure to chemical or physical agents. Symptoms can include itchy or dry skin, a red rash, bumps, blisters, or swelling. These rashes are not contagious or life-threatening, but they can be very uncomfortable.

Epidemiology

Contact dermatitis constitutes 95% of all occupational skin disorders. Accurate statistics on the incidence and prevalence are limited due to methodological differences in studies.

Signs and Symptoms

Contact dermatitis is a localised rash or irritation of the skin caused by contact with a foreign substance. The inflammation affects the epidermis and the outer dermis, leading to large, burning, and itchy rashes that can take several days to weeks to heal. There are differences between irritant contact dermatitis (ICD) and allergic contact dermatitis (ACD):

• Red rash: Immediate in ICD; delayed (24–72 hours) in ACD.
• Blisters or wheals: Often form in a pattern where skin was exposed.
• Itchy, burning skin: ICD tends to be more painful, while ACD often itches.
• Surface appearance of skin: Dry and fissured in ICD; vesicles and bullae in ACD.

Causes

Irritant Contact Dermatitis

ICD results from the direct cytotoxic impact of irritants on epidermal keratinocytes, disrupting the skin barrier and activating the immune system. Common irritants include solvents, metalworking fluids, latex, kerosene, ethylene oxide, certain foods, perfumes, and cleaning products. Physical irritants like low humidity from air conditioning can also cause ICD.

Allergic Contact Dermatitis

ACD is a hypersensitive reaction that requires prior exposure to an allergen. Common allergens include nickel, gold, Balsam of Peru, chromium, and the oily coating from plants like poison ivy. The allergic reaction occurs in two phases: induction (sensitisation) and elicitation (secondary immune response).

Photocontact Dermatitis

This form is triggered by the interaction between a substance on the skin and ultraviolet light (320–400 nm UVA). It manifests only in regions exposed to such rays and can be prevented by avoiding sunlight. Psoralens, used therapeutically for psoriasis, eczema, and vitiligo, are common triggers.

Diagnosis

Diagnosis involves identifying the responsible irritant or allergen, often through patch testing. This test exposes the skin to suspected irritants to check for a reaction. The top three allergens found in patch tests are nickel sulphate, Myroxylon pereirae (Balsam of Peru), and fragrance mix I.

Histology and immunologic findings also aid diagnosis, although they may not distinguish between ICD and ACD conclusively.

Prevention

In industrial settings, employers must provide safety equipment like protective clothing, gloves, or barrier creams. A multidimensional approach includes:

• Identifying potential cutaneous irritants and allergens.
• Using appropriate control measures or substitutes.
• Personal protection with protective clothes or barrier creams.
• Maintaining personal and environmental hygiene.
• Regulating harmful irritants in the workplace.
• Raising awareness through education.
• Promoting safe working conditions and practices.
• Conducting health screenings before, during, and after employment.

Treatment

Self-care

• Cold moist compresses for blistering.
• Calamine lotion and oral antihistamines for itching.
• Avoiding scratching and washing with soap and cool water after exposure.
• Hydrocortisone cream for mild cases.
• Weak acid solutions can counteract effects of basic irritants.
• Barrier creams like zinc oxide can protect and retain moisture.

Medical Care

If self-care is ineffective, medical treatment includes:

• Corticosteroids: Applied as creams or ointments, or taken orally/injected for severe cases.
• Antihistamines: Prescribed if non-prescription strengths are inadequate.

Severe cases may require stronger medications like halobetasol.

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Self-assessment MCQs (single best answer)

What percentage of occupational skin disorders are constituted by contact dermatitis?

Which of the following is NOT a symptom of contact dermatitis?

Which of the following is a common allergen that can cause allergic contact dermatitis?

What differentiates irritant contact dermatitis (ICD) from allergic contact dermatitis (ACD)?

Which treatment is recommended for mild cases of contact dermatitis?

What is the common cause of photocontact dermatitis?

What is the primary method used to diagnose contact dermatitis?

Which of the following is NOT a recommended self-care treatment for contact dermatitis?

Which protective measure is NOT typically recommended to prevent contact dermatitis in occupational settings?

Which substance is commonly used in barrier creams to protect the skin from contact dermatitis?