Blastocystis hominis is a microscopic parasite found in stools of healthy people and also in the stools of people who suffer from diarrhea, abdominal pain or other gastrointestinal problems. A blastocystis infection is called blastocystosis.

Sometimes blastocystis is present in the digestive tract without causing any symptoms or damage. In some cases, the parasite or some subtypes of it can cause an infection or a risk of infection when combined with other types of infection.

There are no specific treatments for bastocystosis and the infection generally clears up on its own. However, if the symptoms are persistent, some medications may be recommended.


Symptoms that may indicate balstocystosis include:

  • Diarrhea
  • Nausea
  • Bloating
  • Excessive gas (flatulence)
  • Abdominal cramps
  • Anal itching
  • Weight loss
  • Loss of appetite
  • Fatigue


Blastocystis is a microscopic single-celled organism (protozoan). The gastrointestinal tract is the home of numerous protozoans some of which can cause diseases.

People can carry blastocystis without showing symptoms but the parasite can also be found in people with diarrhea or other gastrointestinal problems who are more susceptible to infection.

It is unclear whether blastocystis causes disease on its own or combined with other organisms. Experts are unsure how blastocystis is transmitted but a common hypothesis is that blastocystis enters the intestinal tract through oral-fecal contact or poor sanitation and hygiene.

Risk factors

Anyone is at risk of getting blastocystis. At higher risk may be the ones who stay at a place with inadequate sanitation or polluted water.


Diarrhea associated with blastocystis can lead to dehydration due to the loss of fluids and minerals.


Eating safe food

  • Avoid food from street vendors
  • Avoid raw meat, fish and shellfish
  • Avoid unpasteurized milk and dairy products
  • Avoid moist food at room temperature
  • Eat well cooked foods served hot
  • Chew well foods high in sugar or dry foods such as bread
  • Eat fruits and vegetables that be peeled

Caution with water

  • Avoid unsterilized water (tap, well, stream)
  • Avoid ice cubes or fruit juices made of tap water
  • Keep mouth closed while showering
  • Do not swim in contaminated water
  • Avoid sliced fruit washed in contaminated water
  • Mix baby formula with bottled or boiled water
  • Use bottled water to brush teeth
  • Ensure hot beverages are steaming hot

Water can also be chemically disinfected with iodine or chlorine. Iodine tablets are also an option to prevent the risk of infection.

Precautions against transmitting a parasite to others

  • Frequent hand washing: Appropriate hand rinsing with soap and water is important especially after using the toilet.
  • Wash hands well after changing a diaper.