Drug eruptions are diagnosed mainly from the medical history and clinical examination.

In medicine, a drug eruption is an adverse drug reaction of the skin.

The drug eruption can be an expected adverse effect or an unexpected effect (idiosyncratic).

Red man syndrome (Drug eruption)

Drugs causing fixed drug eruptions:

Maculopapular drug eruption due to the Japanese herbal medicine Kakkonto (kudzu or arrowroot decoction).

Abel EA, Farber EM: Drug eruptions and urticaria.

Sandler B, Aronson P. Yohimbine-induced cutaneous drug eruption, progressive renal failure, and lupus-like syndrome.

Dermatitis herpetiformis is often misdiagnosed, being confused with drug eruptions, contact dermatitis, dishydrotic eczema (dyshidrosis), and even scabies.

The disease mimics many other dermatoses and can be confused with conditions, such as sarcoidosis, discoid lupus erythematosus, mycosis fungoides, and fixed drug eruption.

Photoleukomelanodermatitis of Kobori is a cutaneous condition, a dyschromic drug eruption that occurs after ingestion of afloqualone, thiazides or tetracyclines, followed by exposure to sunlight.

AGEP is an acute febrile drug eruption characterized by numerous small, primarily non-follicular, sterile pustules, arising within large areas of edematous erythema.

Warfarin necrosis is also different from another drug eruption associated with warfarin, purple toe syndrome, which usually occurs three to eight weeks after the start of anticoagulation therapy.

A fixed drug eruption is the term for a drug eruption that occurs in the same skin area every time the person is exposed to the drug.

It is estimated that 2-3 percent of hospitalised patients are affected by a drug eruption, and that serious drug eruptions occur in around 1 in 1000 patients.

Examples of common drugs causing drug eruptions are antibiotics and other antimicrobial drugs, sulfa drugs, nonsteroidal anti-inflammatory drugs (NSAIDs), biopharmaceuticals, chemotherapy agents, anticonvulsants, and psychotropic drugs.

Some of the most severe and life-threatening examples of drug eruptions are erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis, hypersensitivity vasculitis, DRESS syndrome, erythroderma and exanthematous pustulosis.

If the diagnosis is in doubt, tests may be performed to rule out similar conditions such as Lyme disease, ringworm, guttate psoriasis, nummular or discoid eczema, drug eruptions, other viral exanthems, and especially secondary syphilis.

Rarely, pseudoephedrine therapy may be associated with mydriasis (dilated pupils), hallucinations, arrhythmias, hypertension, seizures and ischemic colitis; as well as severe skin reactions known as recurrent pseudo-scarlatina, systemic contact dermatitis, and nonpigmenting fixed drug eruption.

Drug-induced lichenoid reactions (also known as "Lichenoid drug eruption" and "Drug-induced lichen planus") are skin eruptions that occur after ingestion, contact, or inhalation of certain chemicals, with the most common inducers being gold salts, beta blockers, antimalarials, thiazide diuretics, furosemide, spironolactone, and penicillamine.

Melanonychia is a black or brown pigmentation of the normal nail plate, and may be present as a normal finding on many digits in black patients, as a result of trauma, systemic disease, or medications, or as a postinflammatory event from such localized events as lichen planus or fixed drug eruption.

Acute generalized exanthematous pustulosis (AGEP) (also known as "Pustular drug eruption," and "Toxic pustuloderma") is a not uncommon cutaneous reaction pattern that in 90% of cases is related to medication administration, characterized by a sudden eruption that appears on average five days after the medication is started.