Cornside patch cannot be used to treat flat warts. Cornside patch is mainly used to treat cornside. The main ingredients of the patch are salicylic acid and phenol. Salicylic acid has the effect of dissolving keratin and phenol has the effect of disinfection and antisepsis. It is a strong irritant to exfoliate the keratin and may cause skin breakdown, infection or scarring when used to treat warts. The patient can apply topical retinoids such as 0.1% retinoic acid cream, or topical imiquimod cream which has antiviral and immune modulating effects. For more stubborn cases, you can also choose to take oral isotretinoin or topical cryotherapy.