Rectal Pain or Itching

Since you have a rash around your anus, this is the likely cause of your itching. Your rash is probably caused by one of the following problems:

Eczema

Eczema is an itchy rash that arises due to local irritants or allergy. A rash or itch around the anus can be caused by certain foods (particularly coffee, tea, cola, chocolate, tomatoes, alcohol, and citrus fruits) or from cosmetic products that are used in the area.

Psoriasis

Psoriasis is a recurring rash caused by a variation in your immune system. It very commonly causes a rash in the buttock crease, and it also most commonly affects the scalp, the ear, the groin, and the elbows and knees. Psoriasis causes the skin to appear red and thickened with a white or silvery crust. Many treatments are effective, ranging from skin creams to light exposure and oral medicines.

"Jock itch" (tinea cruris)

Tinea is a fungus infection of the skin, and it commonly affects the groin, upper thigh, and buttock crease. Tinea of the groin is named "tinea cruris" or jock itch. A tinea infection appears as a bright red or red-brown patch of skin with a well-defined boundary. This rash is very itchy.

Seborrheic dermatitis

Seborrheic dermatitis can cause a greasy red rash with some yellow crusts. If you have seborrheic dermatitis in your buttock crease, you probably have also noticed a similar rash at your scalp line or on your face or chest. Dandruff is a form of seborrheic dermatitis.

Yeast infection (candidiasis)

Yeast infections can cause an itchy or painful red rash on the skin. It is most common for a yeast infection to affect the skin in the folds of the groin (at the top of the thigh) and the skin around the genitals, but it may also occur in the anus area or the buttock crease.

Scabies

Scabies are mites that can infect your skin. Scabies are very contagious. Scabies can cause a rash and itching outside of the groin and buttock area, even if the infestation is localized to this area.

Genital warts

Warts in the genital or anal area can appear like a flat or thin layer when they are closely clustered. Warts are caused by a virus infection with "human papillomavirus." This virus is spread through sexual contact.