Overview
Contact Dermatitis
Quick Reference
Critical Alerts
- Most contact dermatitis is self-limited: Supportive care
- Differentiate from cellulitis: Contact dermatitis is pruritic, not tender
- Severe or widespread may need systemic steroids: 2-3 week taper
- Identify and remove the offending agent: Key to treatment
- Poison ivy/oak/sumac is most common allergic cause: Urushiol
- Watch for secondary infection: Impetiginization
Irritant vs Allergic Contact Dermatitis
| Feature | Irritant | Allergic |
|---|---|---|
| Mechanism | Direct damage | Delayed hypersensitivity (Type IV) |
| Onset | Immediate to hours | 24-72 hours after exposure |
| Location | Limited to contact area | May spread beyond |
| Prior sensitization | Not required | Required |
| Common causes | Soaps, detergents, chemicals | Nickel, poison ivy, fragrances |
Emergency Treatments
| Severity | Treatment |
|---|---|
| Mild | Topical corticosteroids (triamcinolone 0.1%) |
| Moderate | Medium-potency topical steroids + antihistamines |
| Severe/Widespread | Systemic steroids (prednisone 40-60 mg × 2-3 weeks) |
Definition
Overview
Contact dermatitis is an inflammatory skin reaction caused by direct contact with a substance. It is classified as irritant contact dermatitis (ICD)—direct skin damage—or allergic contact dermatitis (ACD)—a delayed-type (Type IV) hypersensitivity reaction. Common causes include chemicals, soaps, nickel, and plants (poison ivy). Treatment involves removing the offending agent and topical or systemic corticosteroids.
Classification
By Mechanism:
| Type | Mechanism |
|---|---|
| Irritant contact dermatitis (ICD) | Direct toxic effect on skin |
| Allergic contact dermatitis (ACD) | Type IV hypersensitivity (T-cell mediated) |
Epidemiology
- Very common: 15-20% of population
- Occupational: Leading cause of occupational skin disease
- ICD accounts for 80%: of contact dermatitis cases
Etiology
Irritant Contact Dermatitis:
| Cause | Examples |
|---|---|
| Soaps, detergents | Hand washing, cleaning |
| Chemicals | Solvents, acids, alkalis |
| Water | Wet work |
| Plants | Non-allergic plant irritants |
Allergic Contact Dermatitis:
| Allergen | Examples |
|---|---|
| Plants (urushiol) | Poison ivy, oak, sumac |
| Metals | Nickel (jewelry, belt buckles) |
| Fragrances | Cosmetics, perfumes |
| Preservatives | Formaldehyde, parabens |
| Rubber | Latex, rubber gloves |
| Topical antibiotics | Neomycin, bacitracin |
Pathophysiology
Irritant Contact Dermatitis
- Direct damage to skin barrier
- No immune sensitization required
- Severity depends on concentration, duration, and substance
Allergic Contact Dermatitis
- Sensitization phase: First exposure; antigen presented to T-cells (1-2 weeks)
- Elicitation phase: Re-exposure triggers T-cell response (24-72 hours)
- Inflammatory response: Cytokine release, eczematous reaction
Clinical Presentation
Symptoms
| Finding | Description |
|---|---|
| Pruritus | Most prominent symptom |
| Erythema | Redness |
| Vesicles/Bullae | May be present (especially ACD) |
| Weeping/Crusting | If vesicles rupture |
| Scaling/Lichenification | In chronic cases |
| Linear or geometric pattern | Suggests external contact |
History
Key Questions:
Physical Examination
| Finding | Significance |
|---|---|
| Well-demarcated borders | Contact pattern |
| Linear streaks | Plant (poison ivy) |
| Under watch/jewelry | Nickel allergy |
| Hands | Occupational, detergent |
| Face | Cosmetics |
| Vesicles | Acute ACD |
| Scaling | Chronic ICD |
New products (soaps, lotions, laundry detergent)?
Common presentation.
Occupational exposures?
Common presentation.
Jewelry (nickel)?
Common presentation.
Outdoor activities (plants)?
Common presentation.
Time course (onset related to exposure)?
Common presentation.
Prior similar episodes?
Common presentation.
Red Flags
Secondary Infection
| Finding | Concern | Action |
|---|---|---|
| Honey-crusted lesions | Impetigo | Antibiotics |
| Purulent drainage | Bacterial infection | Antibiotics |
| Fever | Cellulitis, systemic infection | IV antibiotics |
| Rapidly spreading erythema | Cellulitis | Antibiotics |
Differential Diagnosis
Other Causes of Eczematous Rash
| Diagnosis | Features |
|---|---|
| Atopic dermatitis | Chronic, flexural, atopic history |
| Nummular dermatitis | Coin-shaped lesions |
| Cellulitis | Tender, warm, systemic symptoms |
| Tinea | Annular, KOH positive |
| Psoriasis | Silvery scale, nail changes |
| Herpes simplex/zoster | Grouped vesicles, dermatomal |
Diagnostic Approach
Clinical Diagnosis
- Contact dermatitis is a clinical diagnosis
- History of exposure + characteristic pattern
Patch Testing
- Outpatient: For recurrent or unclear ACD
- Identifies specific allergen
Laboratory/Imaging
- Not routinely needed
- KOH prep if fungal infection suspected
Treatment
Principles
- Identify and remove offending agent: Key step
- Topical steroids: For localized disease
- Systemic steroids: For severe or widespread
- Antihistamines: For itch relief
- Antibiotics: If secondary infection
Remove Offending Agent
- Wash skin with soap and water immediately after plant exposure
- Avoid re-exposure
- Clean clothing and objects that may carry allergen
Topical Corticosteroids
Mild/Localized Disease:
| Agent | Potency |
|---|---|
| Hydrocortisone 1-2.5% | Low (face, folds) |
| Triamcinolone 0.1% | Medium (body) |
| Betamethasone 0.05% | High (palms, soles, severe) |
| Clobetasol 0.05% | Super-high (thick areas) |
Application: BID × 1-2 weeks
Systemic Corticosteroids
Severe or Widespread Disease (e.g., Poison Ivy):
| Regimen | Notes |
|---|---|
| Prednisone 40-60 mg daily × 5-7 days, then taper over 2-3 weeks | Avoid short course (rebound) |
Common Mistake: Short (5-day) prednisone → Rebound dermatitis
Antihistamines
For Itch Relief:
| Agent | Dose |
|---|---|
| Diphenhydramine | 25-50 mg q6h (sedating) |
| Cetirizine | 10 mg daily |
| Hydroxyzine | 25-50 mg q6h |
Soothing Measures
| Intervention | Details |
|---|---|
| Cool compresses | Reduce inflammation |
| Calamine lotion | Soothing |
| Oatmeal baths | Soothing |
| Emollients | Restore skin barrier |
Secondary Infection
| Indication | Treatment |
|---|---|
| Impetigo | Topical mupirocin or oral cephalexin |
| Cellulitis | Oral or IV antibiotics |
Disposition
Discharge Criteria
- Diagnosis confirmed
- Medications prescribed
- Educated on avoidance
- Follow-up arranged if needed
Admission Criteria
- Rarely needed
- Severe bullous reaction with extensive skin loss
- Secondary cellulitis requiring IV antibiotics
Referral
| Indication | Referral |
|---|---|
| Recurrent or chronic | Dermatology, patch testing |
| Occupational | Occupational medicine |
Patient Education
Condition Explanation
- "Your rash is caused by contact with something that irritated or triggered an allergic reaction in your skin."
- "Identifying and avoiding the trigger is the most important step."
- "Steroid cream or pills will help reduce the inflammation."
Prevention
- Avoid known triggers
- Wear gloves if working with irritants
- Learn to identify poison ivy/oak/sumac
- Wash skin immediately after plant exposure
- Use barrier creams
Warning Signs to Return
- Fever
- Spreading redness, warmth
- Pus or honey-crusted sores
- Not improving after 1-2 weeks
Special Populations
Children
- Same treatment principles
- Avoid high-potency steroids on face/folds
Occupational Dermatitis
- Most common occupational skin disease
- May need job modification
- Barrier creams may help
Pregnancy
- Topical steroids generally safe (avoid super-high potency)
- Oral steroids if necessary (short course safe)
Quality Metrics
Performance Indicators
| Metric | Target | Rationale |
|---|---|---|
| Trigger identified | >0% | Key to prevention |
| Systemic steroids tapered (not short course) | 100% | Prevent rebound |
| Differentiated from cellulitis | 100% | Avoid unnecessary antibiotics |
Documentation Requirements
- Suspected trigger
- Distribution of rash
- Presence of vesicles or secondary infection
- Treatment and follow-up
Key Clinical Pearls
Diagnostic Pearls
- Pruritus is hallmark: Differentiates from cellulitis (pain)
- Linear pattern = Plant contact: Poison ivy classic
- Watch/Jewelry = Nickel: Under metal
- Geometric/Well-demarcated = External cause
- ICD is more common but ACD is more memorable
- Patch testing for recurrent/unclear cases
Treatment Pearls
- Wash skin immediately after plant exposure: Removes urushiol
- Topical steroids for localized: Medium potency
- Systemic steroids for widespread: 2-3 week taper required
- Avoid short prednisone courses: Rebound is common
- Antihistamines help itch: But don't treat cause
- Treat secondary infection if present
Disposition Pearls
- Most can be discharged: With topical +/- systemic treatment
- Refer recurrent cases for patch testing
- Educate on trigger avoidance
- Return if signs of secondary infection
References
- Fonacier L, et al. Contact dermatitis: A practice parameter. Ann Allergy Asthma Immunol. 2015;115(6):424-440.
- Usatine RP, Riojas M. Diagnosis and Management of Contact Dermatitis. Am Fam Physician. 2010;82(3):249-255.
- Mowad CM, et al. Allergic contact dermatitis: Patient diagnosis and evaluation. J Am Acad Dermatol. 2016;74(6):1029-1040.
- Gladman AC. Toxicodendron dermatitis: Poison ivy, oak, and sumac. Wilderness Environ Med. 2006;17(2):120-128.
- Shenefelt PD. Herbal Treatment for Dermatologic Disorders. CRC Press. 2011.
- Militello G, et al. An approach to the patient with contact dermatitis. Clin Dermatol. 2020;38(1):9-21.
- NICE Guideline. Contact dermatitis: Management. 2020.
- UpToDate. Allergic contact dermatitis. 2024.