Anal pruritus is a common disease in dermatology. Because of the specific location, although the itch is unbearable, scratching can be embarrassing, so many patients may have had their symptoms for a long time before they visit the doctor. There are various causes of anal itching, and I will analyze them with you below. 1, neurodermatitis: anal neurodermatitis is characterized by paroxysmal severe itching, when the patient will scratch the area until bleeding. As a result of long-term friction and scratching, the skin thickens and becomes leather-like. The skin texture becomes thicker than normal, also known as mossiness. 2. Contact dermatitis: It can be caused by various drugs, aromatic agents of toilet paper or preservatives on wet toilet paper, resulting in allergic contact dermatitis. One study reported that 18 of 40 consecutive patients with the onset of the disease showed a positive patch test. Gastrointestinal contents of spicy condiments, or laxatives, or failure to adequately wipe clean after a bowel movement, can also lead to irritant contact dermatitis, and cause itching. 3, physical factors: for example, hemorrhoids, anal redundancy, fissures and fistulas can aggravate or cause itching. Anatomical factors can lead to rectal mucus leakage and irritation of the perianal skin, and cause itching. 4, venereal disease: anal acral warts and syphilis flat warts can be the cause of anal itching. Anal gonorrhea, especially in men, is often ignored because itching is the only symptom. 5, fungal infection: fungal anal pruritus is characterized by the presence of fissures and a white and moist epidermis. Potassium hydroxide can be used to find fungi after fixing the dermis of the anal area. Candida albicans, Flocculina epidermidis and Trichophyton rubrum are the common causative fungi in the area. Other fungal susceptibility sites, such as the groin, should be examined as well. The use of tetracycline can induce Candida infections leading to anal itching, most commonly in women. Diabetic patients are susceptible to perianal candidiasis. 6. Bacterial infections: Erysipelas in the groin and perianal area can occasionally cause itching, and a coral-red fluorescence under Wood’s lamp can confirm the diagnosis. β-hemolytic streptococcal infections can also grow to be the cause. 7. Parasitic infections: Pinworm infections can cause anal itching, especially in children and sometimes in their parents, with nighttime itching being the most common. Other gastrointestinal parasites such as pork tapeworm and amoeba protozoa can also cause pruritus. Pubic lice can cause anal itching, but the patient’s attention is often focused on the pubic bone. Scabies can be the cause, but also often involves the interphalangeal, wrist, axillary, areola, and genitalia. 8, other skin diseases: seborrheic dermatitis of the anal area can cause anal itching, and the disease can also involve other areas such as the groin, scalp, chest and face. Similarly, lichen planus can also involve the perianal area. Anal psoriasis can be pruritic, with well-defined lesions around the anus, and psoriatic damage can be present on other parts of the body, such as the nails. If you feel that you have anal itching, it is important to go to the hospital for a thorough examination to find the specific cause before applying a reasonable and effective treatment plan.