Contact Dermatitis
Allergic and irritant contact dermatitis evaluation and patch testing.
Overview
Contact dermatitis is an inflammatory skin condition that occurs when the skin comes into contact with a substance that causes an allergic reaction (allergic contact dermatitis) or direct irritation (irritant contact dermatitis). It's one of the most common occupational skin diseases.
types
allergic
Delayed hypersensitivity reaction (Type IV) that occurs 24-72 hours after exposure to an allergen. Requires prior sensitization.
irritant
Direct damage to the skin from exposure to irritating substances. Can occur on first exposure and affects anyone exposed to sufficient concentrations.
symptoms
allergic
- Itchy, red rash
- Blisters that may ooze
- Swelling
- Dry, cracked, scaly skin
- Symptoms typically appear 24-72 hours after exposure
- Rash may spread beyond the contact area
irritant
- Burning or stinging sensation
- Red, inflamed skin
- Dry, cracked skin
- Blisters in severe cases
- Symptoms appear quickly after exposure
- Rash typically limited to contact area
common Allergens
- Nickel (jewelry, metal objects)
- Fragrances and perfumes
- Preservatives (formaldehyde, parabens)
- Rubber and latex
- Poison ivy, oak, sumac
- Hair dyes and cosmetics
- Topical medications (neomycin, bacitracin)
- Metals (chromate, cobalt)
- Adhesives and glues
common Irritants
- Soaps and detergents
- Cleaning products
- Solvents
- Acids and alkalis
- Friction and rubbing
- Water (frequent wetting and drying)
- Dust and fiberglass
evaluation
history
- Detailed history of exposures (occupational, personal care products, hobbies)
- Timing of symptom onset
- Location of rash
- Pattern of symptoms (improves away from work, etc.)
- Recent changes in products or environment
physical
Assessment of rash distribution, pattern, and characteristics
patch Testing
indication
Essential for diagnosing allergic contact dermatitis
process
- Small amounts of common allergens applied to skin
- Left in place for 48 hours
- Read at 48 and 96 hours
- Positive reactions indicate sensitization
common Series
Standard patch test series includes 30-80 common allergens
referral
Refer to dermatologist or allergist for patch testing
differentiation
allergic
Delayed onset, spreads beyond contact area, requires prior sensitization, positive patch test
irritant
Immediate or rapid onset, limited to contact area, affects anyone with sufficient exposure, negative patch test
treatment
immediate
- Remove or avoid the offending substance
- Wash affected area with mild soap and water
- Cool compresses for relief
- Topical corticosteroids for inflammation
- Oral antihistamines for itching
topical
- Topical corticosteroids - appropriate strength based on severity
- Topical calcineurin inhibitors for sensitive areas
- Moisturizers to restore skin barrier
- Calamine lotion for soothing
systemic
- Oral corticosteroids for severe, widespread reactions
- Oral antihistamines for itching
- Antibiotics if secondary infection is present
prevention
- Identify and strictly avoid the trigger
- Use protective gloves and clothing when handling irritants
- Choose fragrance-free, hypoallergenic products
- Read product labels carefully
- Consider barrier creams for occupational exposure
occupational
considerations
- Document work-related exposures
- Consider workers' compensation evaluation
- Workplace accommodations may be needed
- Personal protective equipment
- Job modification or rotation
referral
Refer to occupational medicine specialist for work-related cases
prognosis
With proper identification and avoidance of triggers, contact dermatitis typically resolves within 2-4 weeks. Allergic contact dermatitis requires lifelong avoidance of the allergen once sensitized. Irritant contact dermatitis can improve with reduced exposure and proper skin care.
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