Contact Dermatitis

Contact dermatitis is a delayed hypersensitivity reaction of the skin occurring after direct contact with a chemical or allergen.

• Common triggers include:

  • Dyes

  • Perfumes

  • Rubber

  • Nickel

  • Certain drugs

  • Skin preparations containing lanolin, iodine, antihistamines, or neomycin

• The reaction may be acute or chronic, with varying severity depending on the concentration of the allergen and duration of exposure.

• Pathophysiology involves type IV hypersensitivity, mediated by T-lymphocytes, leading to inflammation, edema, and vesicle formation.

Signs & Symptoms

• Acute phase:

  • Red, papulo-vesicular rash with ill-defined margins

  • Itching, which may be severe

  • Blisters and weeping lesions, sometimes crusted

• Chronic phase (repeated exposure or delayed treatment):

  • Dry, cracked, scaly skin

  • Lichenification (thickened skin)

  • Swelling, burning, or tenderness

• Distribution: Confined to areas of contact with the offending agent, often linear or patterned according to exposure.

Diagnostic Criteria

Diagnosis is clinical, based on history and lesion appearance:

• Red papulo-vesicular rash with ill-defined margins

• Severe pruritus

• Dry, cracked, or scaly skin in chronic cases

• Blisters, draining fluid, or crusting in severe dermatitis

• Swelling, burning, or tenderness at affected sites

Note: Consider patch testing in recurrent or unclear cases to identify the responsible allergen.

Investigation

• Patch testing: Gold standard to identify allergens causing delayed-type hypersensitivity

• Skin biopsy: Rarely required; may help distinguish from other eczematous dermatoses

• Cultures: Only if secondary infection is suspected

Treatment

Management involves eliminating the trigger, supportive care, and pharmacologic therapy.

Non-Pharmacological Treatment

• Avoidance of allergen: Essential to prevent recurrence

• Protective clothing or gloves if exposure is unavoidable

• Gentle skin care:

  • Use mild soaps or emollients

  • Avoid scrubbing or harsh cleansers

Pharmacological Treatment

• Topical corticosteroids (first-line therapy):

  • Betamethasone valerate 0.025% cream/ointment applied 12-hourly for two weeks

  • Super-potent or potent steroids may be needed for severe lesions

Notes on topical therapy:

• A single application at night under occlusion is often more effective than multiple daytime applications

• Avoid long-term continuous use to prevent skin atrophy, striae, or pigmentation changes

• Adjunctive therapy:

  • Wet dressings for acute weeping lesions

  • Oral antihistamines for severe pruritus (e.g., cetirizine or loratadine)

• Secondary infection management:

  • If bacterial infection develops (yellow crusting or pus), consider topical or systemic antibiotics as indicated

Prevention

• Identify and avoid known allergens

• Educate patients on safe handling of chemicals

• Use protective gloves and barrier creams when contact is unavoidable

• Early treatment of minor reactions to prevent chronic dermatitis and lichenification

Complications

• Chronic lichenified skin

• Persistent hyperpigmentation or hypopigmentation

• Secondary bacterial infection

• Reduced quality of life due to pruritus and cosmetic disfigurement

Prognosis

• Acute contact dermatitis usually resolves within 2–3 weeks with proper treatment

• Chronic exposure may lead to relapsing or persistent lesions