Not applicable. This is a manual tool, not a topical product.
Source: Scholl product information.

File dry or slightly damp hard skin using light, even strokes. Work gradually rather than removing everything in one session. Rinse and dry after use.

A simple, durable manual foot file
Shaped handle reaches any area of the foot
Hygienic and washable
No batteries, charging or replacement heads
Works well alongside a urea heel balm

For external use on feet only. Not for use on broken, cracked, irritated or inflamed skin, or over open wounds, moles or warts. Do not over-file - remove hard skin gradually across several sessions. Keep out of reach of children. If you have diabetes, poor circulation or reduced sensation in your feet, do not use without first speaking to your doctor or podiatrist. Discontinue use if the skin becomes sore.