Terbinafine hydrochloride is an allylamine drug with broad-spectrum antifungal activity. This product can specifically interfere with the early biosynthesis of fungal sterols, inhibit fungal squalene cyclooxygenase with high selectivity, and block the epoxidation of squalene during the formation of fungal cell membrane, thus achieving the effect of killing or inhibiting fungi. However, the 86-year-old man is advised not to take terbinafine tablets even if he has all kinds of tinea, because the drug will have adverse reactions, which the old man can't bear.