Defined as a drug reaction that affects the structure or function of the skin, its appendages, or mucous membranes.
Common adverse skin reactions to systemic drugs include: maculopapular skin reactions; urticaria and angio-oedema; and the spectrum of skin lesions including fixed drug eruptions, erythema multiforme, DRESS (drug reaction with eosinophilia and systemic symptoms; also called drug hypersensitivity syndrome), Stevens-Johnson syndrome, and toxic epidermal necrolysis. Together these account for the majority of all drug-induced skin manifestations.
Any drug can cause a predictable or unpredictable reaction; those commonly implicated include beta-lactam antibiotics, muscle relaxants used in anaesthesia, sulfonamides and structurally related drugs, contrast media, and gelatins.
A history of previous reactions to drugs should always be taken before prescribing.
Skin tests (prick tests, intradermal tests, patch tests) can occasionally be useful in diagnosing allergic reactions retrospectively, especially contact dermatitis.
After anaphylactic reactions, serum tryptase activity can help in diagnosis.
Cutaneous drug reactions are common. They are adverse drug reactions (ADRs) producing a wide range of skin manifestations. An ADR may be defined as an undesirable clinical manifestation resulting from administration of a particular drug. Another definition is that of an appreciably harmful or unpleasant reaction resulting from an intervention related to using a medicinal product. An ADR may be either immunological (i.e., drug allergy) or non-immunological (i.e., drug intolerance). Drug allergies are estimated to account for <10% of all adverse drug reactions, with drug intolerance accounting for the other 90%.
Adverse reactions usually predict hazard from receiving the drug in the future and warrant prevention, specific treatment, alteration of the dose regimen, or withdrawal of the product. They range from common irritant eruptions to rare, life-threatening drug-induced diseases.
A serious adverse reaction is any untoward medical occurrence that at any dose: results in death; is life threatening; requires or prolongs hospital admission; requires medical or surgical intervention to preclude permanent impairment of a body function or permanent damage to a body structure; is a congenital anomaly; or is any medical event that would be regarded as serious if it had not responded to immediate treatment.
The most common skin drug eruptions typically present as pruritus, maculopapular eruptions, urticaria, angio-oedema, phototoxic and photoallergic reactions, fixed drug reactions, vesiculobullous reactions, and exfoliative lesions. These manifestations clinically resemble an allergic response and are considered drug hypersensitivity reactions.
Drug reactions can be solely limited to the skin, or they may be part of a systemic reaction.
History and exam
- presence of risk factors
- history of drug exposure
- skin lesions
- variable skin reactions within 5 to 15 minutes of drug exposure
- variable skin reactions within a few hours of drug exposure
- variable skin reactions within 2 weeks of drug exposure
- variable skin reactions within months to years of drug exposure
- previous exposure and reaction to drug
- blood (whole blood, plasma, serum) drug concentration
- serum tryptase concentration (anaphylaxis)
- complement pathway assay
- histology of lesion biopsy
- FBC and differential
- anti-histone antibodies to single-stranded DNA (lupus-like syndrome)
- skin tests (prick tests, intradermal tests, patch tests)
Michael Ardern-Jones, BSc, MBBS, DPhil, FRCP
Faculty of Medicine
University of Southampton
MA-J declares that he has no competing interests.
Dr Michael Ardern-Jones would like to gratefully acknowledge Dr Wei Yann Haw, Dr Anne Holbrook, Dr Hermenio Lima, and Dr Jeffrey K. Aronson, the previous contributors to this topic. WYH, AH and HL declare that they have no competing interests. JKA is editor of Meyler's Side Effects of Drugs and its annual companion volumes, the Side Effects of Drugs Annuals.
Shahbaz A. Janjua, MD
Ayza Skin & Research Center
SAJ declares that he has no competing interests.
Craig K. Svensson, Pharm.D, PhD
College of Pharmacy, Nursing, and Health Sciences
CKS declares that he has no competing interests.
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