Morbilliform eruption due to amoxicillin

Morbilliform (measles-like) eruptions (figure 1) are the most common pattern, but may be indistinguishable from toxic erythema or exanthem due to bacterial or virus infection. Fever and enanthem (mucosal lesions) suggest an infective cause.
Widespread symmetrical erythematous macules (small flat lesions), patches (large flat lesions), papules (small bumps) and/or plaques (large indurated areas) are most prevalent on the trunk and proximal limbs. Itch can be absent, or mild to severe. The skin often peels off as the rash resolves.
Morbilliform eruptions typically develop within two weeks of exposure to the drug. The drug should be stopped to prevent progression to exfoliative dermatitis / erythroderma. Late onset accompanied by eosinophilia, fever and internal organ involvement suggests drug hypersensitivity syndrome, which is fatal in around 8% of cases.
Sometimes the rash resolves despite continuing the responsible drug, and it may not always recur on re-exposure.
Management should include emollients and mild to moderate potency topical steroids. Systemic steroids are not usually required, but are mandatory for drug hypersensitivity syndrome.

The list of possible culprits is too long to list here! Antibiotics are the most common.