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A pinworm infection is one of the most common types of human intestinal worm infections. Pinworms are tiny, narrow worms. They’re white in color and less than half an inch long. A pinworm infection, also known as enterobiasis or oxyuriasis, is the most common type of worm infection in humans in the United States, according to the Centers for Disease Control and Prevention (CDC).
Pinworm infections can spread easily. They’re most common in children between the ages of 5 and 10, people who live in institutions, and those who have regular, close contact with individuals in these groups. An effective treatment for pinworm infections is medication, though reinfection is possible. Serious complications and long-term health effects are rare.
Pinworms infections are highly contagious. You become infected with pinworms by unintentionally ingesting (or inhaling) pinworm eggs, usually deposited by an infected person onto an object. The cycle of infection begins with the ingestion of these microscopic eggs.
Once the eggs enter your body, they remain in the intestine until they hatch and mature. As adults, the female pinworms move into the colon and exit the body through the anus. Female pinworms lay eggs in the folds of skin around the anus. The presence of these eggs often causes anal itching and irritation.
When a person scratches the affected area, the pinworm eggs transfer to the fingers. The eggs can survive for several hours on your hands. If the infected person touches bedding, clothing, toilet seats, toys, or other household objects, the eggs transfer to these objects. Pinworm eggs can survive on these contaminated surfaces for up to three weeks.
Children transfer pinworm eggs easily because they may put infected toys or other objects directly into their mouths. The eggs can also transfer from contaminated fingers directly to food or liquids. While uncommon, it’s also possible for adults to inhale airborne eggs when shaking contaminated bedding, towels, or clothing.
Pinworm infections affect people of all ages and geographical regions. Since the pinworm eggs are microscopic, it’s impossible to avoid infected individuals or areas.
While anyone can get a pinworm infection, the following groups are more susceptible:
Some individuals with pinworm infections may not experience any symptoms. However, you may suspect that you or your child has a pinworm infection if you notice:
A tape test is the most reliable method for diagnosing a pinworm infection. A tape test consists of taking a piece of cellophane tape and pressing the sticky, adhesive side against the skin around the anus. Since pinworms often exit the anus while the infected person sleeps, you should conduct a tape test upon waking in the morning. If eggs are present, they will stick to the tape. Take the tape to your doctor, who can place it on a slide and examine it under a microscope to see if it contains pinworm eggs.
Routine morning activities, such as bathing or using the toilet, can remove eggs from your skin, so the results of a tape test are most accurate if you perform the test when you first wake up. The CDC recommends that you conduct a tape test at least three times, on three consecutive mornings, to increase your likelihood of finding pinworm eggs.
Your doctor can usually treat a pinworm infection effectively with oral medication. Since pinworms pass so easily from one person to another, everyone living in the household of an infected person usually needs treatment at the same time to prevent reinfection. Caregivers and others who have close, personal contact with the individual also receive treatment.
The most common and effective medications to treat pinworm infection are:
One course of medication usually involves an initial dose, followed by a second dose two to three weeks later. More than one course may be necessary to fully eliminate the pinworm eggs. Creams or ointments can soothe itching skin in the area around the anus.
In addition to medication, a specific regimen of hygiene and household cleaning can help you completely eliminate the pinworm eggs. This regimen is below.
Humans are the only pinworm hosts. Your cat or dog can’t infect you or be infected with pinworms. It’s not necessary to treat your pets for the infection.
Most people don’t experience serious complications as a result of pinworm infections. Rarely, if the infestation is left untreated, pinworm infections can sometimes cause a urinary tract infection in women. Pinworms can also travel from the anus into the vagina, affecting the uterus, fallopian tubes, and other pelvic organs. Vaginitis, endometritis (an inflammation of the uterine lining), or other infections may result.
The presence of a significant number of pinworms can cause abdominal pain.
Substantial pinworm populations can rob your body of essential nutrients, which can cause weight loss.
The best way to prevent pinworm infections and reinfections is to follow recommended hygiene routines and encourage other household members, especially children, to do the same. You can work to prevent pinworm infections with several practices, including:
It’s possible to eradicate a pinworm infection with medication and the recommended cleaning regimen. However, because pinworm eggs are invisible to the naked eye and are highly contagious, reinfection can easily occur. A person can reinfect themselves or become reinfected by eggs from another person. If you experience recurrent infections after you have treated your household, individuals and locations outside of the household may be the primary source of the pinworm eggs.
Written by: Anna Giorgi
Medically reviewed on: Feb 18, 2016: Steve Kim, MD
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