Worm infections (intestinal helminths)

Overview

Worm infections happen when parasitic worms (helminths) live in the intestine. The most common ones spread through soil and are called soil-transmitted helminths. They are roundworm (Ascaris), whipworm and hookworm. A fourth soil worm, Strongyloides, needs different tests and a different medicine. Threadworms (also called pinworms) are another common type, especially in children. They spread easily within families.

Worm eggs pass out in the faeces (poo) of an infected person. Where there are no proper toilets, the eggs get into soil and water. People swallow them on unwashed fruit and vegetables, in dirty water, or from dirty hands. Hookworm babies (larvae) live in soil and get in through bare skin, usually when people walk barefoot. Threadworm eggs stick to fingers after scratching and then to bedding, toys and food.

The World Health Organization estimates that about 1.5 billion people, nearly a quarter of the world, carry soil worms. They are most common in warm countries with poor sanitation. Children and women of childbearing age are hit hardest. People with only a few worms usually feel well. A heavy load of worms can cause belly pain, diarrhoea, blood loss and anaemia (low red blood cells), and can slow a child's growth and learning. Deworming medicines are cheap, safe and work well, but worms can come back if hygiene and sanitation do not improve.

Symptoms

• Often no symptoms at all, especially when there are only a few worms
• Belly pain, bloating, feeling sick, vomiting or poor appetite
• Diarrhoea that comes and goes; whipworm can cause diarrhoea with blood or mucus (dysentery)
• Tiredness, weakness and pale skin from anaemia, mainly with hookworm
• Weight loss or poor growth in children
• Seeing worms in the poo or vomit; threadworms look like small pieces of white thread in the poo or around the bottom
• Strong itching around the bottom or vagina at night, with poor sleep, waking and irritability (threadworms)
• Cough, wheezing, breathlessness or fever for a short time when roundworm larvae pass through the lungs

Causes and risk factors

Causes

• Roundworm (Ascaris), whipworm and hookworm, whose eggs pass out in human faeces and contaminate soil
• Swallowing worm eggs on unwashed or unpeeled fruit and vegetables, in dirty water, or from hands soiled with earth
• Hookworm larvae in the soil getting in through bare skin, mainly the feet
• Threadworm eggs moving from the bottom to fingers when scratching, then to clothes, bedding, toys, surfaces and food, and being swallowed
• Strongyloides, another soil worm, which can multiply inside the body and needs its own treatment

What makes it more likely

• Living where there are no proper toilets, people go to the toilet in the open, or human waste is used as fertiliser
• No safe drinking water and few chances to wash hands
• Being a young child or a school-age child
• Being a woman of childbearing age, including during pregnancy and breastfeeding
• Walking barefoot on soil, or work with heavy soil contact such as tea-picking or mining
• Living in a warm, damp climate
• Eating raw vegetables and keeping animals at home, which were linked with worms in schoolchildren in north-west Pakistan
• Living with a child or family member who has threadworms

Complications

Hookworms feed on blood, and worms take iron and protein from the body, so heavy infection can cause anaemia, especially in teenage girls and women. In pregnancy this anaemia is linked with low birth weight and a higher risk of death for mother and baby. In children, long-term infection can cause malnutrition and slow physical growth and learning. A large mass of roundworms can block the intestine, mainly in children, and may need surgery. Roundworms can also move into the bile duct or pancreas and cause infection or pancreatitis (swelling of the pancreas), and they are linked with appendicitis. Heavy infection can also make the back passage slip out (rectal prolapse). In people with weak immunity, Strongyloides can spread through the whole body, and this is almost always fatal without quick, proper treatment.

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Diagnosis

Most worm infections are found by testing a stool (poo) sample under a microscope for worm eggs. Sometimes adult worms are seen in the poo or vomit, which makes the cause clear. In early infection the test can miss the worms, so a repeat sample may be needed. During the lung stage of roundworm, a blood test may show raised eosinophils (a type of white blood cell). If worms are thought to be in the bile duct or blocking the bowel, the doctor may order an ultrasound or CT scan. Strongyloides needs different tests and is often missed.

Threadworms are often recognised when white threads are seen around the bottom or in the poo at night, and a pharmacist can supply treatment. In places where worms are common, WHO advises giving deworming medicine regularly to children and other at-risk groups without testing each person first.

Treatment

1. See a doctor or pharmacist if you think you or your child has worms. Tell them if you are pregnant or breastfeeding, if the child is under 2, or if you have a weak immune system.
2. For roundworm, whipworm, hookworm and threadworm, the usual treatment is a short course of deworming medicine, most often albendazole or mebendazole. It works well whatever the type of worm. Your doctor decides the dose.
3. For threadworms, treat everyone in the home over 2 years old at the same time, even if they have no symptoms, and follow strict hygiene. The medicine kills the worms but not the eggs.
4. If Strongyloides is found, the doctor will use ivermectin, because albendazole and mebendazole do not work against it well.
5. In pregnancy, do not self-treat. The doctor weighs the risk to the baby against the risk of untreated worms and chooses the medicine and the timing.
6. Worms often come back where soil and water are contaminated, so your doctor may advise another treatment later and the whole family should improve hygiene.
7. A blocked bowel or worms in the bile duct are treated in hospital and may need an endoscopy (a camera tube) or surgery.

Medicines in Pakistan

Medicines a doctor may use, by group. Read the role: some are only for special cases. Each link opens our page for that medicine, with every brand and its official DRAP price. Your doctor decides which medicine and dose are right for you.

Also used (not yet in our price list): Nitazoxanide (used less often for roundworm), Piperazine (sometimes used for roundworm in pregnancy when needed)

Self-care and prevention

Self-care

• Wash hands with soap after using the toilet and before cooking or eating
• Keep nails short and clean, and try to stop children biting nails or sucking fingers
• For threadworms: shower every day, and wash sleepwear, bedding and towels in hot water
• For threadworms: do not shake bedding, share towels or bite nails, and clean surfaces often
• Keep up these hygiene steps for 2 weeks after medicine, or for 6 weeks if medicine cannot be used
• Children with threadworms do not need to stay off school, and adults do not need to stay off work
• Take the deworming medicine as your doctor or pharmacist explains, and make sure the whole family is treated when advised

Prevention

• Always use a toilet or latrine and never let faeces get into soil or water
• Drink safe water
• Wash, peel or cook fruit and vegetables before eating them
• Wear shoes outdoors, especially on soil that may be dirtied by faeces, to prevent hookworm
• Wash hands before handling food and after using the toilet
• Take part in school and community deworming programmes for children and women

Common questions

Does the whole family need deworming medicine?

For threadworms, yes: everyone in the home over 2 years old should be treated at the same time, because the eggs spread easily. Roundworm, whipworm and hookworm do not pass directly from person to person, but family members often catch them from the same soil, food or water. Ask your doctor or pharmacist who needs treatment.

Can I take worm medicine during pregnancy?

Only on a doctor's advice. WHO includes pregnant women in the second and third trimesters in deworming programmes, but some medicines, such as ivermectin, are not used in pregnancy. Your doctor will balance the risk to the baby against the harm from untreated worms, such as anaemia.

Why do the worms keep coming back?

The medicine kills the worms but not always the eggs, and new eggs can be picked up from soil, water, food or hands. Good hand-washing, safe water, clean toilets and wearing shoes are the best way to stop it happening again. In areas where worms are common, repeat treatment is often needed.

Are deworming tablets safe for children?

WHO says albendazole and mebendazole have been given to millions of people with few and mild side effects. They are used in school deworming programmes around the world. For children under 2, ask a doctor or pharmacist first.

Sources

1. World Health Organization. Soil-transmitted helminth infections (2023).
2. CDC. About Soil-transmitted Helminths (2024).
3. CDC. Clinical Care of Soil-transmitted Helminths (2024).
4. NHS 111 Wales. NHS 111 Wales - Health A-Z : Threadworms (2024).
5. StatPearls (NCBI Bookshelf). Ascariasis (2026).
6. Saudi Journal of Biological Sciences (Khan W et al.). Risk factors associated with intestinal pathogenic parasites in schoolchildren (2022).

Prepared from the sources listed below by the MedInfoBase team. Last reviewed 16 October 2026. This page is general health information, not medical advice. It gives no doses and does not replace a doctor: talk to your doctor or pharmacist before starting, stopping or changing any medicine. How we write and check our pages.

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