No, the treatment doesn´t hurt when the product is used correctly and in accordance to the user instructions. EndWarts PEN contains formic acid and has, in the treatment of warts, a dehydrating effect. However, formic acid in itself is corrosive and needs to be handled with extra care. If the solution comes in contact with skin surrounding the wart, the skin can be damaged. If it should burn or sting when treating, rinse the wart/verruca with cold water and do not apply any more solution. It has already penetrated the wart/verruca. Never cover the wart with plasters during treatment with EndWarts PEN.