drug rash, a skin eruption, usually an allergic reaction, that is caused by a particular drug. Nearly any drug can produce a skin reaction as a result of gradual accumulation of the drug or development of antibodies that reject a component of the medication. A drug rash that is a sensitivity reaction does not occur the first time the drug is taken; the effect is observed with subsequent uses. Also called dermatitis medicamentosa. See also fixed drug eruption.
