Last reviewed: 25 Sep 2021
Last updated: 20 May 2020



History and exam

Key diagnostic factors

  • 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

Other diagnostic factors

  • pruritus
  • associated non-cutaneous features
  • pain

Risk factors

  • virus infections
  • HIV infection
  • HLA-B*5701 polymorphism
  • HLA-B*1502 polymorphism
  • HLA-B*5801 polymorphism
  • female sex

Diagnostic investigations

Investigations to consider

  • 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)

Emerging tests

  • drug-specific IgE
  • basophil activation test
  • lymphocyte proliferation assay (LPA/LTT)
  • enzyme-linked immunospot assay (ELISPOT test)

Treatment algorithm



Michael Ardern-Jones, BSc, MBBS, DPhil, FRCP

Associate Professor

Consultant Dermatologist

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.

Peer reviewers

Shahbaz A. Janjua, MD

Specialist Dermatologist

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

Purdue University

West Lafayette



CKS declares that he has no competing interests.

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