Contact dermatitis

Question 1

Acute contact (exogenous) dermatitis can be either

Answer 1

irritant or allergic

Question 2

Features:

Answer 2

itchy, inflamed skin

red and swollen

papulovesicular

may be dry and fissured

Question 3

Causes

Answer 3

Irritant contact dermatitis: caused by primary irritants e.g.

• acids
• alkalis
• detergents
• soaps

Allergic contact dermatitis (~80%): caused by:

allergens that provoke an allergic reaction in some individuals only

most people can handle the chemicals without undue effect.

• photocontact allergens.
• 4.5% of population is allergic to nickel
• 1–3% to an ingredient in cosmetics.

Question 4

Common allergens

Answer 4

• Ingredients (fragrances) in cosmetics (e.g. perfumes, preservatives)
• Topical antibiotics (e.g. neomycin)
• Topical anaesthetics (e.g. benzocaine)
• Topical antihistamines
• Plants (skin of mango cross-reacts with these): rhus, grevillea, primula, poison ivy
• Metal salts (e.g. nickel sulphate, chromate)
• Dyes esp. clothing dyes
• Hairdressing chemicals
• Glutaraldehyde (e.g. sterilising agent)
• Rubber/latex
• Resins
• Toluene sulfonamide compound resin (e.g. nail polish)
• Coral

Question 5

Management

Answer 5

Determine cause with vigour and remove it

• Patch testing helps confirm diagnosis. Consider usage test.

Wash with water (only) and pat dry (avoid soap)

Oral prednisolone for severe cases:

• 25–50 mg/d for 1–2 wks
• then reduce gradually over 1–2 wks

Topical corticosteroid cream

• moderate to potent
• depending on site

For chronic phase use fragrance-free moisturisers regularly

• e.g. glycerol 10% in sorbolene cream.