Fixed drug eruptions (FDEs) occur suddenly within 30 minutes to 8 hours of ingesting the offending substance. Because many medications are ingested at bedtime, it is common for the patient to relate a history of retiring with clear skin and first discovering the eruption upon arising.
Initially, there is usually a single lesion at one site. With continued exposure, additional lesions develop and other anatomic areas may also become active. Although new sites may develop, the original site will reactivate with each episode of exposure, and the limitation of the reaction to that site is a striking feature. These attacks occur on a cyclical basis with the frequency determined by the usage pattern of the offending agent.
Once the lesions arise, they reach their maximum activity within a few hours. The acute lesions consist of red or violet-brown dermal macules and, on occasion, palpable plaques with vesicles or bullae. Patients complain of a burning discomfort or a deep-seated itch that cannot be relieved by rubbing or scratching. The acute inflammatory phase lasts 7 to 10 days, then gradually resolves. FDE typically causes a long lasting gray-brown hyperpigmentation, which increases with subsequent episodes.
The only provoking factors are ingested foreign substances, which are almost exclusively prescription or proprietary medications. On rare occasions foods are implicated, producing a "fixed food reaction." The list of offending agents is extensive. The following list includes the more common offenders, but is not all-inclusive.
Was this article helpful?