Erythrodermia to pseudoephedrine in a patient with contact allergy to phenylephrine

Phenylephrine and pseudoephedrine are sympathomimetic drugs belonging to the phenylamine family. Adverse cutaneous effects associated with these drugs have been reported but, in view of their frequent use, appear to be rare. The very close chemical structures of these drugs could explain potential cross-reactions among them but the results reported in the literature are controversial.

An 18-year-old woman developed blepharoconjunctivitis after application of phenylephrine and tropicamide eye drops. Four years after this reaction, she took 1 tablet of Narine (pseudoephedrine and loratadine) and 3-4 hours later developed a generalized erythrodermic reaction. Cutaneous biopsy revealed hydropic changes in the basal layer and, in the dermis, moderate edema with slight perivascular lymphocyte and eosinophil infiltrates. Patch tests with European standard series, commercial eye drops, tropicamide, phenylephrine, pseudoephedrine and other sympathomimetic agents were applied to the patient's back. After 47 and 96 hours, only the patches with pseudoephedrine and phenylephrine were positive.

We believe that our patient has presented two different reactions with different clinical outcome and histopathology, which are unlikely to be due to cross-reactivity between the drugs involved. We have found no similar coincidences reported int the literature.