Pinworm Infection

How pinworm infection spreads

1. Eggs are swallowed, usually from contaminated fingers.
2. They hatch in the small intestine, and worms mature in the large bowel over 1 to 2 months.
3. At night, adult females crawl out of the anus to lay thousands of sticky eggs on the surrounding skin.
4. The eggs cause itching. Scratching transfers eggs under fingernails, which then reach the mouth, food, toys, bedding and surfaces.
5. Eggs can survive on surfaces for up to 2 to 3 weeks.

Pinworms only infect humans. Pets do not spread them. Infection is common in all social groups and is not a sign of poor hygiene.

Symptoms

Many people have no symptoms. When present:

• Itching around the anus, especially at night (anal itching)
• Disturbed sleep, restlessness and irritability, which can look like insomnia
• Vaginal itching and discharge in girls, when worms move to the vulva (vulvovaginitis)
• Seeing worms: tiny white threads around the anus at night or in stool
• Skin irritation or broken skin from scratching. Other causes of anal itching include hemorrhoids and anal fissures
• Occasionally mild abdominal discomfort or bedwetting

Pinworms rarely cause serious problems. Rare complications include skin infections, urinary tract infections in girls, and very rarely worms in the female reproductive tract.

Diagnosis

• Look for worms: shine a flashlight on the anal area 2 to 3 hours after a child falls asleep. Worms look like moving white threads.
• Tape test: first thing in the morning, before bathing or using the toilet, press clear sticky tape against the skin around the anus, then stick it to a slide or bag it for the clinic. Repeat on 3 consecutive mornings to increase accuracy.
• Fingernail samples occasionally.

Stool tests are not useful because eggs are laid on the skin rather than in stool.

Treatment

Medicines

The second dose after 2 weeks kills worms that hatched from eggs swallowed after the first dose. Household members are usually treated at the same time, because many are infected without symptoms.

Ask a doctor before treating children under 2 years or during pregnancy or breastfeeding; hygiene measures alone may be advised initially in pregnancy.

Soothing itching

• Wash the area gently with water in the morning
• A mild barrier cream such as zinc oxide may soothe irritated skin. Avoid scented products that can cause contact dermatitis
• Keep nails short to reduce damage from scratching

Hygiene measures to prevent reinfection

These are as important as the medicine:

• Wash hands with soap and water after using the toilet, before eating and after changing diapers
• Scrub under fingernails and keep nails short
• Discourage nail biting and thumb sucking
• Bathe or shower every morning to remove eggs laid overnight
• Change underwear daily and wear close-fitting underwear at night
• Wash pajamas, bedding and towels in hot water on the day of treatment and regularly for the following weeks
• Do not shake bedding, which spreads eggs into the air
• Clean toilet seats, door handles and toys regularly
• Vacuum floors and clean surfaces in bedrooms and bathrooms
• Do not share towels or washcloths

Children can usually go to school or childcare after the first dose of treatment.

Frequently asked questions

What are the symptoms of pinworms?

The main symptom is itching around the anus, especially at night, leading to disturbed sleep and irritability. Girls may have vaginal itching. You may see tiny white thread-like worms around the anus at night. Many people have no symptoms.

How do you get rid of pinworms?

Take one dose of pyrantel pamoate (over the counter), albendazole or mebendazole, then repeat after 2 weeks. Treat the whole household at the same time. Strict hygiene, including handwashing, short nails and washing bedding, prevents reinfection.

How do you get pinworms?

You get pinworms by swallowing their microscopic eggs, which are spread from an infected person's fingers to surfaces, food, bedding and toys. Children often reinfect themselves by scratching and then putting their fingers in their mouths.

Can adults get pinworms?

Yes. Adults often catch pinworms from infected children, especially parents and caregivers. Symptoms are the same: nighttime anal itching. Adults in the household are usually treated at the same time as the child.

Why do pinworms keep coming back?

Reinfection is common because eggs survive on surfaces for up to 3 weeks and spread easily within households. Not treating all family members, skipping the second dose, or lapses in handwashing and laundry can lead to recurring infection.