There are two main possibilities for itching on the back of the feet, one is tinea pedis and the other is eczema. Tinea pedis is caused by fungal infection, and you need to test for fungus before treatment. If the fungus is positive, the diagnosis can be confirmed, and you can use topical terbinafine hydrochloride ointment, naftifine ketoconazole cream, terbinafine hydrochloride spray, and in severe cases, you can take oral terbinafine hydrochloride tablets or itraconazole capsules. Another possibility is eczema, which is caused by allergy. You can apply topical mometasone furoate ointment, denide ointment, hydrocortisone butyrate ointment, and take oral levocetirizine hydrochloride tablets or loratadine tablets. If the disease is severe, you can take oral compound glycyrrhizin capsules or even IV compound glycyrrhizin injection. You need to avoid spicy and stimulating diet, beef, mutton, seafood and other hairy products, and alcoholic beverages in your daily life.