Wells syndrome following vaccination: A pediatric case with positive patch test to gelatin.

We report a 12-month-old boy with a skin eruption that developed 15 days after receiving the measles, mumps, rubella (MMR), pneumococcal, and meningococcal vaccines, consistent with the diagnosis of Wells syndrome. Patch testing showed a positive reaction to gelatin, which is used as a stabilizer for both live and inactivated vaccines. Gelatin was only present in the MMR vaccine.