The pinworm, also known as threadworm, is a very common intestinal parasite. The medical condition associated with pinworm infestation is known as enterobiasis.
According to the Centers for Disease Control and Prevention (CDC), pinworms are the most common type of worm infection in the United States.
They are parasites, meaning that they use the human body to survive and reproduce. Human pinworms cannot infect any other animals.
Adult worms are just 0.2 to 0.4 inches or 5 to 10 millimeters (mm) in length, about the size of a staple. They are white or cream colored and look like small pieces of thread. Pinworms can live for up to 6 weeks.
This MNT Knowledge Center article will explore the causes, symptoms, and treatments in more detail.
- The worms mature in the intestine and then move through the digestive system to lay eggs, at night, in the anal area.
- The itchiness tends to be worse or more noticeable at night, and can sometimes wake a person with pinworms.
- A pinworm can lay thousands of microscopic eggs.
- Pinworm eggs are not visible to the naked eye.
If an individual only has a small number of adult worms, the symptoms will be mild, or there may be no symptoms at all. Symptoms are worse with heavy or moderate infections.
About 4 weeks after ingesting pinworm eggs, the mature females make their way out from the intestine to the anal area, where eggs are laid in a jelly-like substance.
It is this substance that is believed to cause a person to itch, which usually happens at night. During the maturing and reproduction stages, a person with pinworms may experience:
- disturbed sleep
- itching of the anal area, which may sometimes be intense, especially at night when the female worms are laying eggs
- mild nausea
Individuals with severe infection may experience:
- loss of appetite
- severe irritability
- intermittent abdominal pain
- sleeping difficulties
- weight loss
If somebody is found to have an infection, all other members of the household should be treated too, even if they have no symptoms.
Strict hygiene measures can remedy pinworm infection and significantly reduce the risk of re-infection.
The worm has a life span of about 6 weeks, so any hygiene measures taken need to last at least that long.
Everyone in a household with pinworms must adhere to the following:
- Wash all bed linen, bedclothes, and cuddly toys. A normal washing temperature is acceptable, but it needs to be well-rinsed.
- Vacuum the home thoroughly, especially the bedrooms. Vacuuming needs to be regular and thorough throughout the 6-week period.
- Damp-dust surfaces in the kitchen and bathroom, washing the cloth often in hot water regularly.
- Do not shake things that may have eggs on them, such as clothing, pajamas, bed linen, or towels.
- Do not eat in the bedroom. There is a risk of swallowing eggs that have shaken off the bedclothes.
- Make sure the fingernails of every member of the household are cut short.
- Refrain from nail biting and finger sucking. This may not be easy if there are small children in the house.
- Wash your hands thoroughly and frequently, and scrub under the fingernails. Before eating, after going to the toilet, and after changing diapers, make sure to wash hands.
- At night, wear close-fitting underwear. Be sure to change underwear every morning.
- Cotton gloves may help prevent scratching during sleep.
- Take a bath or shower regularly. Thoroughly clean the body, paying particular attention to the anal and vaginal areas. Showering is preferred to avoid contaminating bath water.
- Do not share towels or face flannels.
- Toothbrushes should be kept in a closed cupboard and rinsed well before use.
When the infestation has gone, good hand-washing practice and hygiene will help prevent re-infection. Good hygiene can prevent another outbreak even if children pick up another pinworm infection from friends at school.
The cause of pinworm infection is inadequate hygiene.
Eggs are transferred from the anus of an infected person to either their own mouth, re-infecting themselves, or another surface. If somebody else touches that contaminated surface and then touches their mouth, they may have ingested the eggs and can become infected.
The female pinworm lays eggs around the anus and vagina. The eggs can be transferred from the person's anus to:
- bed sheets
- underwear and clothes
The female pinworm releases an itchy mucus when laying her eggs, triggering an urge to scratch the affected area of the anus or vagina. From the hands, the eggs may be transferred to anything that is touched, including:
- bathroom utensils, such as toothbrushes, combs, and brushes
- directly to other people's hands
- kitchen and bathroom surfaces
- kitchen utensils
Swallowing the eggs
The eggs can survive for up to 3 weeks on surfaces. If they are touched, they will be transferred to the hands. If the hands then touch the person's mouth, there is a serious risk of swallowing the eggs and becoming infected.
Breathing in the eggs
The microscopic eggs may become airborne and then be breathed in and swallowed. This can happen when shaking towels or bed sheets, for example. The eggs hatch in the intestines 1 to 2 months after being swallowed. After hatching, a female pinworm can lay more eggs.
Poor hygiene among children
Small children are more likely to become infected because they tend to be less thorough about hand washing. Children may also have long-lasting infections because they are swallowing fresh eggs continually.
Children are usually in close contact with each other, making re-infection more likely.
Pinworms are more common in crowded conditions.
Pinworms that affect humans cannot infect animals or pets. However, some microscopic eggs may land on a pet's fur and then be transferred to human hands when petting or playing with them. It is important to remember that the problem is not the pet; it is down to human hygiene.
The following methods can be used to diagnose pinworms:
This test uses cellophane tape. The doctor places a piece of clear plastic tape against the skin around the anus and then looks at the tape under a microscope. As the worm tends to lay her eggs at night, good samples are more likely early in the morning. People may apply the tape themselves before using the bathroom or bathing. The sample should then be taken to the doctor.
A doctor or nurse may take a moistened swab from around the anal area.
Sighting a worm
Sometimes the worms are visible in the anal area, underwear, or in the toilet. In stools, the worms look like small pieces of white cotton thread. Because of their size and white color, pinworms are difficult to see. The male worm is rarely seen because it remains inside the intestine. It is best to search for pinworms at night, when the female comes out to lay her eggs. If you are checking children, it is best to inspect about 2 to 3 hours after they have fallen asleep.
When to see a doctor
If you are pregnant, breast-feeding, or have a baby less than 6 months of age, and you suspect you may have pinworms, you should see your doctor straight away.
Pinworm infection can be easily treated. It is important to remember that treatment also focuses on preventing re-infection. All members of the family need to be treated. Treatment may consist of either a 6-week strict hygiene method or medication followed by strict hygiene for 2 weeks.
Some medications are available OTC (over the counter) at local pharmacies. It is important to follow the manufacturer's instructions. Individuals who are pregnant, breast-feeding, or have a baby less than 6 months old should speak with a doctor.
Medication for pinworms
If medication is used, it should be given to everybody in the household. There is a risk of transmission between family members (people in the same household); so the chances of being infected if somebody has been diagnosed are high, even if no symptoms are present. Currently, the CDC recommends the following treatment for pinworms.
- Mebendazole: This medication blocks the worm's ability to absorb glucose, effectively killing it within a few days. It can be taken in chewable form or as a liquid. A 100 milligrams dose is taken and usually repeated in 2 weeks.
- Pyrantel pamoate: This medication is available over the counter for the treatment of pinworms. It paralyzes the worms. The dose is taken and repeated in 2 weeks.
- Albendazole: Like mebendazole, this medication also blocks the worm's ability to absorb glucose. One 400 milligram dose is taken then repeated in 2 weeks.
Hygiene measures should be continued for the 2 weeks following the initial treatment.
Various medications are available to purchase online. Speak to a doctor before taking any medicaton.
Pregnancy and breastfeeding
The hygiene method is usually recommended for pregnant or breast-feeding mothers, rather than medication. Neither mebendazole or albendazole should be taken during the first 13 weeks of pregnancy.
During the 2nd and 3rd trimesters of pregnancy and breast-feeding, medication can be used if necessary. This decision should be made by a doctor.
Pyrantel should not be taken during pregnancy without approval by a doctor.
Infants and Children
Talk to a doctor for children under 2 who need treatment. The hygiene method is often preferred. If another treatment is necessary, they can recommend the medicine that is appropriate and safe for the child's age.
Though uncomfortable and sometimes alarming, complications as a result of pinworm infection are rare. However, if they do occur, they can include:
- Urinary tract infection: This is more common in females with a heavy pinworm infestation. The worm may also migrate to the bladder, causing cystitis.
- Peritoneal cavity infection: In females, the worm may migrate from the anal area into the vagina and to the uterus, fallopian tubes, and around the pelvic organs, causing vaginitis or endometritis.
- Weight loss: If the infection is severe, the parasite may leech essential nutrients, resulting in weight loss.
- Skin infection: The itching may lead to intense scratching, which might break the skin, raising the risk of infection.
- Appendicitis: There are cases of pinworms migrating into the appendix.
Medication will be required for serious infections or complications. Prevention is usually achievable through adequate hygiene measures. There are no serious or immediately life-threatening complications. As long as treatment occurs soon after symptoms appear, pinworms are parasites that can be easily handled.