What is anal pruritus?

Anal pruritus, also called itching or itching in the anus, is a very common condition that tends to cause a lot of discomfort and embarrassment. Itching in the anus is a symptom, not a disease itself. The itching can be in the anus itself or in the skin around it, it can be transient or persistent and can be accompanied by pain when defecating or performing anal hygiene.

About 5% of the adult population suffers from anal itching, most of the causes being benign and easily treated. Anal itching happens mainly due to excessive sweating, exaggerated intake of irritating foods to the digestive system or the presence of feces in the anal area.

What causes itchy anus (anal pruritus)?

Classically associated with the presence of worms, anal itching can be caused by a number of other diseases and conditions. In general, any situation that causes inflammation or irritation of the anus and perianal area can cause itching. These are some of the most common causes of anal itching:

Inadequate hygiene after evacuation

When hygiene is not done properly, remains of feces can come into contact with the skin and mucosa of the anus. Feces are naturally acidic, with an average pH of 6.6. Prolonged contact with the skin causes irritation and can itself trigger itching without any other illness being present.

The process is similar to that which occurs in babies who wear diapers and have an irritated anal area. On hot days, in addition to feces, the perianal region can also become wet from perspiration, which further favors irritation. Patients with frequent diarrhea or fecal incontinence are especially prone to diaper rash and anal itching, as skin contact with feces is more frequent.

Intense cleaning after evacuation

Although the anal area should be cleaned after each bowel movement, this cleaning should be gentle. Aggressive scrubbing, especially with toilet paper, soaps, or other cleansers, can irritate the skin and cause itching in the perianal area. Remember, any irritation in the perianal area can cause itching.

Reduced anal sphincter pressure

The anal sphincter is the muscle responsible for keeping the anus closed. Some patients with anal itching have a more relaxed sphincter than normal, allowing small leaks of feces and mucus into the perianal region.

In these patients, stool-stimulated anal irritation may occur even if adequate post-defecation hygiene is performed, as leaking occurs intermittently throughout the day. These individuals need to clean the anus more often, not just after a bowel movement.

Diet that contains foods or drinks that irritate the anus

Specific foods such as coffee, tomatoes, beer, soft drinks, tea, peanuts, dairy products, citrus fruits, chocolate and grapes, to name just a few examples, have been associated with anal itching. Once a patient eats or drinks something that might irritate their anus, there is usually a 24- to 36-hour delay before anal itching begins. This is how long it takes for food to travel through the entire digestive tract. Food can cause itching in the anal area by two mechanisms:

⦁ They may not be completely digested and cause irritation on direct contact with the skin in the perianal area after defecation.
⦁ They are irritants or stimulants at the intestinal level, increasing the contact of the feces with the anal mucosa by increasing the frequency of bowel movements or the amount of mucus present in the feces.

Allergy to cleaning and hygiene products

In susceptible people, some chemicals or drugs applied to the anal area may cause local irritation or allergic reactions. Common examples are perfumes or dyes used in some brands of toilet paper, feminine hygiene sprays, baby powder, and soaps, especially scented ones.

Medicines

Just as some foods can cause anal itching in certain individuals, certain types of medications can have the same effect. Colchicine, quinidine, peppermint oil, local anesthetics and neomycin are the most commonly described drugs. Antibiotics in general, but especially tetracycline and erythromycin, can cause perianal itching by interfering with the normal bacterial flora of the intestines and anal area.

Worm

Itching of the anus is a classic symptom of oxyuriasis, worms caused by the helminth Enterobius vermicularis or Oxiurus vermicularis. The itch is usually more intense at night and can make the patient restless and have difficulty sleeping.

Adult worms can migrate to places beyond the anus, such as the vagina and vulva region, eventually causing vaginal itching and discharge. Other types of worms do not usually cause anal itching.

STD

Individuals who engage in passive anal sex may acquire sexually transmitted diseases with anal symptoms. HPV (anal wart), herpes genialis, syphilis and gonorrhea are examples of STDs that can cause anal itching.

Other infections

Fungal infections, particularly candidiasis, scabies (scabies), pubic pediculosis (boring), perianal streptococcal dermatitis, and erythrasma (infection with the bacterium Corynebacterium minutissimum) are examples of infections that can also cause anal itching.

Hemorrhoids

External hemorrhoids are usually associated with bleeding and pain when defecating. In some cases, however, anal itching is the most obvious symptom.

Other anorectal diseases

In addition to hemorrhoids, other diseases of the anus and rectum can cause itching, such as anal fissures, fistulas, abscesses and even tumors.

Dermatological diseases

In the same way that dermatological diseases can cause itching on the skin, they can also affect the perianal region. Examples:

⦁ Contact dermatitis.
⦁ Inverse psoriasis.
⦁ Atopic dermatitis.
⦁ Hidradenitis suppurativa.
⦁ Lichen planus.
⦁ Seborrheic dermatitis.