Drugs can cause multiple skin eruptions and reactions. The most serious of these are discussed elsewhere in THE MANUAL and include Stevens-Johnson syndrome and toxic epidermal necrolysis, hypersensitivity syndrome, serum sickness, exfoliative dermatitis, angioedema, anaphylaxis, and drug-induced vasculitis.
Drugs can also be implicated in hair loss, lichen planus, erythema nodosum, pigmentation changes, systemic lupus erythematosus, photosensitivity reactions, pemphigus, and pemphigoid. Other drug reactions are classified by lesion type.
Symptoms and Signs of Drug Eruptions and Reactions
Symptoms and signs vary based on the cause and the specific reaction (see table Types of Drug Reactions and Typical Causative Agents).
Photo provided by Thomas Habif, MD.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Image courtesy of Anar Mikailov, MD, FAAD.
Photo provided by Thomas Habif, MD.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY
Image courtesy of Anar Mikailov, MD, FAAD.
Diagnosis of Drug Eruptions and Reactions
Clinical evaluation and drug exposure history
Sometimes skin biopsy
A detailed history is often required for diagnosis, including recent use of over-the-counter drugs. Because the reaction may not occur until several days or even weeks after first exposure to the drug, it is important to consider all new drugs and not only the one that has been most recently started.
No laboratory tests reliably aid diagnosis, although biopsy of affected skin is often suggestive.
Sensitivity can be definitively established only by rechallenge with the drug, which may be hazardous and unethical in patients who have had severe reactions. Occasionally, patch testing can be helpful in patients with fixed drug eruptions.
Treatment of Drug Eruptions and Reactions
Discontinuation of offending drug
Sometimes antihistamines and corticosteroids
Most drug reactions resolve when drugs are stopped and require no further therapy. Whenever possible, chemically unrelated compounds should be substituted for suspect drugs. If no substitute drug is available and if the reaction is a mild one, it might be necessary to continue the treatment under careful watch despite the reaction.
Pruritus and urticaria can be controlled with oral antihistamines and topical corticosteroids. For IgE-mediated reactions (eg, urticaria), desensitization can be considered when there is critical need for a drug.
Key Points
Because drugs can cause a wide variety of reactions, drugs should be considered as causes of almost any unexplained skin reaction.
Base the diagnosis primarily on clinical criteria, including a detailed history of prescription and over-the-counter drugs.
Stop the suspected offending drug and treat symptoms as needed.
