Ethylene oxide can effectively sterilise permanent marker pens after repeated use on dogs

To assess the effectiveness of Ethylene oxide sterilisation (EtO) of commercially available permanent marking pens (Sharpie® Permanent Marker Fine Point) following repeated clinical use on canine skin.

A prospective experimental study was conducted using five permanent marker pens. Each pen was used to draw a 5-cm line on the aseptically prepared skin of 10 client-owned dogs consecutively. Pens were sterilised with EtO at the start of the study and between uses. Culture swabs were collected from pen shafts, tips and caps at 3 time points following 1, 6 then 11 sterilisation cycles (S₁, S₆ and S₁₁).

Bacterial growth was detected from the pen tips immediately after use on the first patient prior to resterilisation (S₁), however, no bacterial or fungal growth was identified on tips, shafts or caps after use on 5 patients and after 6 sterilisation EtO cycles. However, after use on 10 patients and 11 EtO sterilisation cycles, a single colony of Staphylococcus capitis was recovered from the pen shafts.

Ethylene oxide appears to be effective at sterilising commercially available permanent marker pens following repeated use on canine skin. Effective sterilisation was maintained through 6 EtO sterilisation cycles.

Ethylene oxide sterilisation may allow safe reuse of permanent marker pens in veterinary practice, supporting sustainable surgical workflows by reducing clinical waste and associated costs.