Acute ICD

• Immediate onset
• Acids/alkaline solutions
• Example: chemical burn

Delayed ICD

• Idiosyncratic reaction, 8-24 hours after exposure
• Anthralin (dithranol), benzalkonium chloride (preservative/disinfectant), ethylene oxide
• Burning ˃ pruritus, sensitivity to touch and water, mimics ACD

Irritant reaction

• Sub-acute to chronic, resolves if exposure stops
• Wet work
• May mimic dyshidrotic dermatitis
• Can result in cumulative ICD
• Scaling, redness, vesicles, pustules, erosions on upper limbs

Cumulative ICD

• Chronic, multiple sub-threshold skin insults without sufficient time to repair with weak irritants
• Lichenification and hyperkeratosis, pruritus, fissures, erythema, vesicles

Asteatotic dermatitis

• Subacute-chronic
• Dry winter months, elderly
• Culprits: water, soaps
• Eczema craquelé

Traumatic ICD

• After acute skin trauma, weeks-months
• Culprits: strong soaps, detergents
• Eczematous

Pustular and acneiform ICD

• Individuals with prior acne, seborrheic dermatitis, atopic dermatitis 🡪 folliculitis and acne
• Culprits: metals, oils, greases, naphthalenes

Non-erythematous ICD

• Subclinical ICD

Subjective or sensory ICD

• Can be reproduced in double-blind exposure tests
• Culprits: Propylene glycol, hydroxy acids, ethanol, sorbic acid and topical medications
• Stinging or burning in absence of visible signs cutaneous irritation

Airborne ICD

• Culprits: Floating dusts, fibers, volatile solvents and sprays
• Simulates photoallergy, but involves upper eyelids, philtrum, submental

Frictional ICD

• Repeated low-grade frictional trauma (e.g. working with paper)
• Hyperkeratosis, acanthosis, lichenification

Contact urticaria

• Non-immunologic:
  • Culprits: Caterpillars, jellyfish, stinging nettles, foods, sorbic acid, benzoic acid (eye drops), cinnamic aldehyde (cosmetics/fragrance)
  • Treatment: NSAIDs (PGD2 mediated)
• Immunologic (previous sensitization):
  • Parabens (preservatives), henna, ammonium persulfate (oxidizing agent), and latex
  • Tx = antihistamines