What is it?

Contact dermatitis is inflammation of the skin caused by direct contact with irritating substances or allergens. It manifests as red, itchy, and sometimes blistering rashes at the site of contact. There are two main types: irritant contact dermatitis (80% of cases), caused by direct chemical damage to the skin, and allergic contact dermatitis (20% of cases), resulting from an immune reaction to specific allergens. This common condition affects millions worldwide and, while not life-threatening, can significantly impact quality of life and work productivity.

Who is affected?

Contact dermatitis affects people of all ages, with certain groups at higher risk.

Prevalence: Affects 15-20% of the general population at some point; accounts for 5-10% of all dermatology consultations
Occupational impact: Represents 70-90% of all occupational skin diseases; costs billions in lost productivity annually
Age patterns: Can occur at any age; allergic type more common in adults; irritant type common in infants (diaper dermatitis) and elderly (thin skin)
Gender differences: Women more commonly affected due to increased exposure to cosmetics, jewelry, and household chemicals
High-risk occupations: Healthcare workers, hairdressers, construction workers, food handlers, cleaners, mechanics, gardeners

What causes it?

Different mechanisms underlie the two main types:

Irritant contact dermatitis: Direct damage to skin barrier by chemicals; disruption of lipid layer and protein denaturation; common irritants include soaps, detergents, solvents, acids, alkalis; cumulative effect from repeated low-level exposure
Allergic contact dermatitis: Type IV delayed hypersensitivity reaction; initial sensitization phase (10-14 days) creates memory T-cells; re-exposure triggers inflammatory response within 24-72 hours; over 3,700 identified allergens
Common allergens: Metals (nickel #1 - affects 17% of women, 3% of men); fragrances and preservatives in cosmetics; rubber chemicals (gloves, shoes); plants (poison ivy/oak/sumac, affecting 50-70% of US population); topical medications (neomycin, benzocaine)
Risk factors: Damaged skin barrier (eczema, cuts) increases penetration; genetic factors influence susceptibility; environmental factors (humidity, temperature); occupational exposures

What are the clinical features?

Contact dermatitis presents differently depending on type and severity:

Irritant contact dermatitis (80%): Immediate burning or stinging upon contact; redness, dryness, cracking, and scaling; well-demarcated area matching contact site; hands most commonly affected (70% of cases)
Allergic contact dermatitis (20%): Delayed reaction (24-72 hours after exposure); intense itching predominant symptom; redness, swelling, vesicles or blisters in acute phase; may spread beyond initial contact area
Distribution patterns: Geometric or linear patterns suggest external contact; face and eyelids from cosmetics or airborne allergens; hands from occupational or household exposures; feet from shoes or socks
Chronic changes: Thickened, leathery skin (lichenification) from repeated scratching; hyperpigmentation or hypopigmentation; fissures and painful cracks
Common presentations by allergen: Nickel - earlobes, wrists, belt line; poison ivy - linear streaks; cosmetics - face, especially eyelids; rubber - hands, feet

How is it diagnosed?

Diagnosis combines clinical assessment with specialized testing:

Clinical history: Detailed exposure history crucial - occupation, hobbies, products used; temporal relationship between exposure and symptoms; pattern and distribution of rash; previous episodes and treatments
Physical examination: Characteristic distribution patterns; morphology varies from acute (vesicles) to chronic (lichenification); noting specific sites affected guides allergen identification
Patch testing (gold standard for allergic type): Standard series of 36-80 common allergens; applied to back for 48 hours, read at 48 and 96 hours; identifies causative allergen in 50-70% of suspected cases; additional specialized series for occupations
Other tests: Repeat open application test (ROAT) for unclear cases; photo-patch testing for photoallergic reactions; skin prick testing not useful (for immediate allergies, not contact)
Differential diagnosis: Atopic dermatitis, seborrheic dermatitis, psoriasis, fungal infections, drug eruptions

What treatment options are available?

Management focuses on avoiding triggers and controlling inflammation:

Avoidance (most important): Identify and eliminate causative agent; substitute with hypoallergenic alternatives; protective equipment (gloves, barriers) when avoidance impossible
Topical corticosteroids (first-line): High-potency for thick skin (palms, soles) - clobetasol; medium-potency for body - triamcinolone; low-potency for face, genitals - hydrocortisone; apply twice daily for 2-4 weeks
Skin barrier restoration: Liberal use of fragrance-free emollients; apply immediately after bathing; petroleum jelly for severe dryness
Symptomatic relief: Oral antihistamines for itching (limited efficacy); cool compresses for acute weeping lesions; oatmeal baths for widespread involvement
Systemic therapy (severe cases): Oral prednisone taper over 2-3 weeks for extensive disease; cyclosporine, methotrexate for chronic recalcitrant cases; dupilumab showing promise in trials
Prevention strategies: Education about allergen sources and cross-reactions; workplace modifications; barrier creams before exposure; proper hand hygiene technique
Prognosis: Excellent if allergen identified and avoided; irritant type resolves within days to weeks after exposure stops; allergic type may persist weeks despite avoidance; chronic hand dermatitis develops in 5-10% despite treatment; occupational change required in 20% of work-related cases

Key points for patients

Contact dermatitis is not contagious and cannot spread to others
Identifying and avoiding triggers is more important than any treatment
Patch testing can identify specific allergens to help prevent future reactions
When to seek medical attention: Severe blistering or widespread rash; signs of infection (pus, fever, red streaks); face or genital involvement; rash not improving after 2 weeks of treatment; recurring episodes affecting daily life
Prevention tips: Read product labels carefully; test new products on small skin area first; wear protective gloves for housework; choose fragrance-free, hypoallergenic products; keep skin moisturized to maintain barrier function

Contact Dermatitis