Contact dermatitis is an inflammation of the skin that can be acute or chronic that manifests as eczematous dermatitis due to exposure to substances in the environment.

Allergic contact dermatitis is an immunologic cell-mediated skin reaction to exposure to antigenic substances.
The lesions initially appear on the cutaneous site of principal exposure then may spread to other more distant sites due to contact or autosensitization. Lesions are typically asymmetrical and unilateral.
Specific signs and symptoms will depend on the duration, location, degree of sensitivity and concentration of allergens. The patch test shows reaction to allergen.
Irritant contact dermatitis is a non-immunologic skin reaction to skin irritants.
It is often localized to areas of thin skin eg eyelids, intertriginous areas.


Allergic Contact Dermatitis (ACD)

  • Initially, lesions appear on the cutaneous site of principal exposure; may spread to other more distant sites due to contact or autosensitization
  • Lesions are typically asymmetrical & unilateral
  • Specific signs & symptoms will depend on the duration, location, degree of sensitivity & conc of allergens
  • Patch test shows reaction to allergen
Irritant Contact Dermatitis (ICD)
  • Often localized to areas of thin skin eg eyelids, intertriginous areas

Signs and Symptoms

Allergic Contact Dermatitis

Acute Allergic Contact Dermatitis

  • Acute eruptions present w/ macular erythema, papules, vesicles & bullae

Chronic Allergic Contact Dermatitis

  • Lesions are usually lichenified, scaling, fissures w/ or w/o vesicles
  • Pigmentary changes can occur

Irritant Contact Dermatitis (ICD)

Acute Irritant Contact Dermatitis

  • Acute lesions are painful, weepy & vesicular

Chronic Irritant Contact Dermatitis

  • Chronic lesions are dry, erythematous, cracked & lichenified
  • Hardening & adaptation of the skin may occur due to repeated contact w/ irritants

Risk Factors

Determine Trigger Factors for Allergic Contact Dermatitis/Irritant Contact Dermatitis
Common Trigger Factors

  • ACD
    • Medications, certain plants, metals, foods, fragrances, stabilizers in skin products, preservatives, etc 
  • ICD
    • Strong alkaline soaps, organic solvents, acid, etc

Location of inflammation may suggest trigger factors for Allergic Contact Dermatitis & Irritant Contact Dermatitis

  • Eg scalp & ears
    • Possible trigger factors: Shampoo, hair dyes, topical medication, spectacles, metal earrings, etc

Allergic Contact Dermatitis & Irritant Contact Dermatitis may be related to occupational exposure

  • Exposure to cement, epoxy, glues, paint & solvents may trigger ACD
  • Fuels, lubricants & cement may trigger ICD
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