Cutaneous Drug Eruptions
Definition
Any drug-induced skin rash, usually allergic in nature
Typically develops ~10 days after drug initiation
Severity spectrum: Mild rashes → Severe Cutaneous Adverse Reactions (SCAR)
Types of Drug Eruptions
Morbilliform Drug Eruption: Measles-like, most common
Urticaria/Angioedema: May occur, but anaphylaxis is rare
Photosensitive Rashes: Drug-induced sunburn-like reaction
Fixed Drug Eruption (FDE): Recurrent rash at the same site
Drug-Induced Pigmentation: Persistent skin & mucosal discolouration
Severe Cutaneous Adverse Reactions (SCAR)
Drug Hypersensitivity Syndrome (DRESS)
Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN)
Aetiology & Causes
Mechanism | Description | Examples |
True Allergy (Immune-Mediated) | IgE-mediated (immediate) or T-cell mediated (delayed) | Immediate: Urticaria, anaphylaxis Delayed: Morbilliform rash, DRESS, SJS/TEN |
Pharmacological Reaction | Expected side effects | Warfarin necrosis, corticosteroid-induced acne |
Drug Intolerance | Exaggerated response | Aspirin sensitivity |
Pseudoallergy | Non-immune mast cell activation | Opioids, NSAIDs |
Management
General Approach
Immediate drug cessation
Symptomatic relief:
Topical corticosteroids (e.g. betamethasone dipropionate 0.05%) for redness & itch
Emollients to maintain skin moisture
Oral antihistamines for itch relief
When to Hospitalise? (Suspected SCAR)
Extensive skin involvement (erythroderma)
Fever, malaise
Mucosal lesions (mouth, eyes, genital areas)
Blisters, pustules, skin pain or tenderness
Organ involvement (e.g. liver, kidney, lungs)
Note:
Drug eruptions + persistent fever/organ dysfunction → Urgent referral (DRESS risk!)
Types of Drug Eruptions & Management
Type | Key Features | Common Causes | Management |
Morbilliform Drug Eruption | Pink/red macules & papules, bilateral & symmetrical, 5–10 days post-drug | Antibiotics (penicillins, cephalosporins), NSAIDs, allopurinol, anticonvulsants | Stop drug, topical steroids, emollients |
Fixed Drug Eruption (FDE) | Round/oval red/violaceous plaques, recur at same site, may blister | Antimicrobials, NSAIDs (e.g. tetracyclines, penicillins, sulfonamides) | Stop drug, topical steroids, avoid re-exposure |
Photosensitivity | Sunburn-like, eczematous/vesiculobullous rash after UV exposure | Doxycycline, NSAIDs, chlorpromazine | Avoid sun, stop drug, sunscreen |
Drug-Induced Pigmentation | Hyperpigmentation, persists post-drug | ACTH, minocycline, amiodarone | Stop drug (pigment may persist) |
DRESS (Drug Hypersensitivity Syndrome) | Fever, rash, lymphadenopathy, organ involvement | Antibiotics, anticonvulsants | Hospitalisation, stop drug, supportive care |
SJS/TEN | Fever, painful red skin, conjunctivitis, blisters, skin detachment | Antibiotics (esp. sulfonamides), anticonvulsants, NSAIDs | Immediate hospitalisation, stop drug, supportive care |
Notes
Morbilliform rash = most common drug eruption
Fixed drug eruption → same site recurrence
DRESS = systemic involvement (rash + fever + internal organ dysfunction) → admit
SJS/TEN = medical emergency!
Always stop the causative drug & use supportive management
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