This article is for general information only and is not medical advice. If you think you have an infection, speak to a pharmacist or your GP.
The short answer
With the right treatment, most gut parasite infections seen in the UK clear within days to a couple of weeks. The medicine itself is usually taken for 1 to 3 days. What takes longer is the hygiene routine that stops you catching the same infection again.
You will often read that it takes 30 to 60 days. That figure comes from herbal cleanse programmes, not from medical guidance, and we explain where it comes from below.
How long treatment takes, by infection
Threadworms
Threadworms are common in children and spread easily. According to the NHS, a pharmacist can recommend medicine (mebendazole), and everyone in the household aged 2 and over should be treated, even if they have no symptoms.
The medicine kills the worms but not their eggs, and the eggs can live for up to 2 weeks outside the body. That is why strict hygiene for 2 weeks matters as much as the medicine. If you cannot take the medicine, for example during pregnancy, the same hygiene measures need to be followed for 6 weeks. Speak to a pharmacist, midwife or GP first if you are pregnant or breastfeeding, or if the person with worms is a child under 2.
Roundworm, hookworm and tapeworm
These are much less common in the UK and are usually picked up abroad. The NHS says a GP may ask for a poo sample, and will then prescribe medicine that you take for 1 to 3 days. Any worms in your gut will eventually pass out in your poo, and you may not notice this. Go back to the GP if your symptoms do not improve within 2 weeks or you keep passing live worms.
Giardiasis
Giardiasis is a tummy bug caused by a microscopic parasite. It is diagnosed from a poo sample and treated with antibiotics. The NHS says symptoms usually stop within about a week, although they can sometimes last longer. Go back to your GP if you still have symptoms a week after starting treatment.
Where does 30 to 60 days come from?
Herbal parasite cleanses are usually sold as 30 to 60 day programmes. The reasoning given is that herbs need to be taken for longer than the life cycle of the parasite, so that newly hatched worms are caught as well.
The problem is that no good-quality human trials show these programmes clear a parasite infection in the first place, so there is no evidence-based length for them. Taking herbs for a month or more also has its own risks. Wormwood, for example, is only recommended for up to 2 weeks at a time. We cover this in clove, black walnut hull and wormwood: what the research says.
If you have been on a cleanse for weeks and still feel unwell, that is a reason to see your GP, not to keep going.
Why infections sometimes come back
The most common reason is catching the infection again. Threadworm eggs spread easily around the home on hands, bedding, towels and surfaces. The NHS recommends that everyone in the household should:
- wash hands and scrub under fingernails, particularly before eating, after using the toilet and after changing nappies
- keep fingernails short
- shower every morning
- wash sleepwear, sheets, towels and soft toys at a hot temperature
- disinfect kitchen and bathroom surfaces
- vacuum and dust with a damp cloth
- avoid shaking clothing or bedding, sharing towels or flannels, and biting nails
When to see a pharmacist or GP
See a pharmacist if you have small white worms in your poo that look like pieces of thread, or extreme itching around your bottom, particularly at night.
See a GP if you:
- find a large worm, a piece of worm or worm eggs in your poo
- have a red, itchy, worm-shaped rash on your skin
- have sickness, diarrhoea or a stomach ache for longer than 2 weeks
- are losing weight for no reason
Tell the GP if you have been abroad in the last 2 years, because some infections take a long time to cause symptoms.