Colloidal silica-induced hypersensitivity: myth or reality

Background Many excipients have been reported to induce drug hypersensitivity (e.g. colouring additives, preservatives). Colloidal silica has never been reported to induce drug hypersensitivity reactions. Case report We report herein a 40-year-old patient who developed a skin eruption 2 days after Voltarene^® (diclofenac) intake, confirmed by a positive patch test. Investigation of cross reactivity, assessed by patch testing to other non steroidal anti-inflammatory drugs, have showed a positive reaction only to piroxicam (Piroxen^®), ketoprofen (Oki^®) and indometacin (Indocid^®). A hypersensivity to colloidal silica, a common excipient, was suspected. A patch test to this compound was performed showing a positive reaction. Conclusion Colloidal silica, a compound widely used in drug manufacturing, could be another culprit excipient in inducing skin hypersensitivity reactions.