Itchy anus can also be due to undigested food like citrus
fruits, grapes, certain spices, tomatoes, certain medicines like antibiotics
and laxatives
and certain drinks like beer, milk, tea, or coffee. Anal fissures, hemorrhoids, threadworms can all cause anal itch. Itch can also be due to irritants like synthetic fiber, toiletries or fungal infection. Genital warts and sores of herpes should also be ruled out. Eczema, dermatitis and fungal infection can also cause this.