Drugs can cause multiple skin eruptions and reactions. The most serious of these are discussed elsewhere in THE MANUAL and include Stevens-Johnson syndrome Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) Stevens-Johnson syndrome and toxic epidermal necrolysis are severe cutaneous hypersensitivity reactions. Drugs, especially sulfa drugs, antiseizure drugs, and antibiotics, are the most common... read more 
and toxic epidermal necrolysis Stevens-Johnson Syndrome (SJS) and Toxic Epidermal Necrolysis (TEN) Stevens-Johnson syndrome and toxic epidermal necrolysis are severe cutaneous hypersensitivity reactions. Drugs, especially sulfa drugs, antiseizure drugs, and antibiotics, are the most common... read more , hypersensitivity syndrome Drug Hypersensitivity Drug hypersensitivity is an immune-mediated reaction to a drug. Symptoms range from mild to severe and include rash, anaphylaxis, and serum sickness. Diagnosis is clinical; skin testing is occasionally... read more , serum sickness Symptoms and Signs Drug hypersensitivity is an immune-mediated reaction to a drug. Symptoms range from mild to severe and include rash, anaphylaxis, and serum sickness. Diagnosis is clinical; skin testing is occasionally... read more , exfoliative dermatitis Erythroderma Erythroderma is defined as erythema that covers more than 70% of the body surface area. It represents the maximum severity of various skin disorders. Diagnosis is by history and examination... read more 
, angioedema Angioedema Angioedema is edema of the deep dermis and subcutaneous tissues. It is usually an acute mast cell–mediated reaction caused by exposure to drug, venom, dietary, pollen, or animal dander allergens... read more 
, anaphylaxis Anaphylaxis Anaphylaxis is an acute, potentially life-threatening, IgE-mediated allergic reaction that occurs in previously sensitized people when they are reexposed to the sensitizing antigen. Symptoms... read more , and drug-induced vasculitis Cutaneous Vasculitis Cutaneous vasculitis refers to vasculitis affecting small- or medium-sized vessels in the skin and subcutaneous tissue but not the internal organs. Cutaneous vasculitis may be limited to the... read more 
.
Drugs can also be implicated in hair loss Alopecia Alopecia is defined as loss of hair from the body. Hair loss is often a cause of great concern to the patient for cosmetic and psychologic reasons, but it can also be an important sign of systemic... read more 
, lichen planus Lichen Planus Lichen planus is a recurrent, pruritic, inflammatory eruption characterized by small, discrete, polygonal, flat-topped, violaceous papules that may coalesce into rough scaly plaques, often accompanied... read more 
, erythema nodosum Erythema Nodosum Erythema nodosum is a specific form of panniculitis characterized by tender, red or violet, palpable, subcutaneous nodules on the shins and occasionally other locations. It often occurs with... read more 
, pigmentation changes Overview of Pigmentation Disorders Melanin is the brownish pigment responsible for the color of skin, hair, and the iris of the eyes. It is produced by melanocytes. Most people have similar numbers of melanocytes, and the wide... read more 
, systemic lupus erythematosus Systemic Lupus Erythematosus (SLE) Systemic lupus erythematosus is a chronic, multisystem, inflammatory disorder of autoimmune etiology, occurring predominantly in young women. Common manifestations may include arthralgias and... read more 
, photosensitivity reactions Photosensitivity Photosensitivity is a cutaneous overreaction to sunlight. It can be related to photoallergy or phototoxicity and may be idiopathic or occur after exposure to certain toxic or allergenic drugs... read more 
, pemphigus Pemphigus Vulgaris Pemphigus vulgaris is an uncommon, potentially fatal, autoimmune disorder characterized by intraepidermal blisters and extensive erosions on apparently healthy skin and mucous membranes. Diagnosis... read more 
, and pemphigoid Bullous Pemphigoid Bullous pemphigoid is a chronic autoimmune skin disorder resulting in generalized, pruritic, bullous lesions in older patients. Mucous membrane involvement is rare. Diagnosis is by skin biopsy... read more 
. Other drug reactions are classified by lesion type (see Table: Types of Drug Reactions and Typical Causative Agents Types of Drug Reactions and Typical Causative Agents 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... read more 
).
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 Types of Drug Reactions and Typical Causative Agents 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... read more ).
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 Biopsy Diagnostic tests are indicated when the cause of a skin lesion or disease is not obvious from history and physical examination alone. These include Patch testing Biopsy Scrapings Examination... read more 
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 Desensitization Drug hypersensitivity is an immune-mediated reaction to a drug. Symptoms range from mild to severe and include rash, anaphylaxis, and serum sickness. Diagnosis is clinical; skin testing is occasionally... read more can be considered when there is critical need for a drug.
If anaphylaxis Anaphylaxis Anaphylaxis is an acute, potentially life-threatening, IgE-mediated allergic reaction that occurs in previously sensitized people when they are reexposed to the sensitizing antigen. Symptoms... read more occurs, treatment is with aqueous epinephrine (1:1000) 0.2 mL subcutaneously or IM, parenteral antihistamines Treatment Anaphylaxis is an acute, potentially life-threatening, IgE-mediated allergic reaction that occurs in previously sensitized people when they are reexposed to the sensitizing antigen. Symptoms... read more , and with the slower-acting but more persistent soluble hydrocortisone 100 mg IV, which may be followed by an oral corticosteroid for a short period.
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.
