Wartner Corn & Callus Removal Pen Wartner Corn & Callus Removal Pen contains TCA gel which is less concentrated compared to the Wartner Verruca & Wart Removal Pen. As corns & persistent calluses have a different cause, a specific treatment is needed. TCA gel peels off excessive skin resulting in the fast removal of corns & persistent calluses. The TCA gel induces a peeling of the skin. As this occurs, the thickened skin / corn will disappear & new healthy skin will form. Easy to use 4 step Application: Hold the pen vertically with the brush tip facing downwards. Slowly turn/click the dial on the top of the Pen clockwise to dispense the gel. Allow the gel to flow into the brush tip for 3 to 5 seconds. Carefully apply the dispensed gel only on the corn or callus (avoid touching healthy skin surrounding it). If accidently applied on surrounding skin, please wash off immediately. Let the gel dry for 10-15 minutes before putting on clothes or shoes.