Adverse drug reaction of the skin

Aetiology

Immunologically mediated reactions ('allergic')

• Not dose dependent
• Type I: anaphylactic reactions, urticaria
• Type II: cytotoxic reactions, pemphigus and pemphigoid
• Type III: immune complex mediated reactions, purpura/rash
• Type IV: T cell mediated delayed hypersensitivity reactions, erythema/rash

Non immunological reactions ('non-allergic')

• Can be dose dependent

• Eczema

• Drug-induced alopecia

• Phototoxicity

• Skin erosion due to topical 5-flurouracil

• Atrophy due to topical corticosteroids

• Psoriasis

• Pigmentation

• Cheilitis, xerosis

Risk factors for drug eruptions

Patient risk factors

• Young adults greater risk than infants/elderly
• More common in females
• Genetic influence
• Concomitant disease - viral infections (HIV, EBV, CMV), cystic fibrosis
• Immune status - previous drug reaction or positive skin test

Drug risk factors

• Chemistry - β-lactam compounds, NSAIDS, high molecular weight/hepten-forming drugs
• Topical route