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Is Blastocystis Hominis Bad? Risks, Treatments & Testing

Written by Helen Quach, BS (Biochemistry) | Last updated:

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Dangers of Blastocystis Hominis
Blastocystis Hominis is a parasite that can cause problems in the intestine. It may cause other health problems or it might not have any symptoms at all. Read more below to learn all about this pathogen and the effects it might have on your body.

What is Blastocystis Hominis?

Blastocystis Hominis is a parasite that can be found all around the world. There are as many as 17 Blastocystis subtypes and they are all genetically diverse [1].

It can infect humans’ intestines and cause diarrhea, nausea, and abdominal pain [2].  

However, people infected by Blastocystis Hominis might not have any symptoms at all and be rid of the pathogen without any treatment. People’s reactions to this parasite depend on the strength of the immune system and the parasite itself [1].

You can get tested for Blastocystis infection by your physician.     

How Can People Get Blastocystis Hominis?

Blastocystis can be found in all parts of the world, from industrialized countries to underdeveloped ones. However, it is prevalent in third world countries due to poor hygiene, contaminated food or water, or contact with animals [2].

It is also possible to be infected through improper food handling. In Iran, infected food handlers caused the consumers who ate their food to be infected as well [3].

Animal handlers also have a higher chance of parasite infection compared to normal. In one study, 41% of animal handlers had Blastocystis infection compared to the control population, where only 5% had it [4].

It is the most common parasite found in stool samples in the United States [2].

Conditions Associated with Blastocystis Hominis

1) Blastocystis Causes Intestinal Problems

Blastocystis causes intestinal problems in many ways – it increases intestinal permeability, degradation of the skin barrier, and causes other toxic effects through cytokine release [1].

Some problems include diarrhea, abdominal pain, nausea, bloating, and flatulence. It might also be linked to irritable bowel syndrome (IBS), but there is not enough evidence to explain how the parasite can cause IBS [2].

2) Blastocystis Causes Skin Problems

Blastocystis might also cause skin problems like itching, redness, and hives (urticaria) [1].

3) Blastocystis Can Cause Thyroid Problems

One male patient who was infected with Blastocystis was found to have Hashimoto’s thyroiditis, a thyroid condition, even though he did not show any symptoms of it. After treatment for Blastocystis Hominis, his thyroid hormones returned to normal [5].

4) Blastocystis Hominis Can Cause Iron Deficiency in Pregnant Women

Pregnant women can be at risk for iron deficiency anemia. Intestinal parasitic infection can increase the risk of iron deficiency.

In one study, women who were found to have Blastocystis Hominis in their intestines were more likely to have iron deficiency anemia than women who were not infected [6].

5) Blastocystis Hominis Lowers Magnesium Levels

Magnesium is an important mineral that helps the body function. Blastocystis Hominis was shown to lower magnesium levels in humans [7].

Should You Be Worried if You Have Blastocystis Hominis?

Stress can increase the effects and symptoms of Blastocystis infection [8].

If an individual has Blastocystis Hominis but they do not exhibit any symptoms, then they do not require treatment. However, it may be possible that there are other bacteria and pathogens in their intestines, so they should get more tests done [2].

If the person does exhibit symptoms, then it is recommended that they undergo treatment with antibiotics [1].

It is important that immunocompromised patients, like people suffering from HIV or cancer, be treated if they are infected [8].


1) Metronidazole

Metronidazole is the most commonly prescribed antibiotic for treating Blastocystis Hominis infection and has a success rate of more than 80%. Metronidazole induces programmed cell death in Blastocystis [9].

However, in some patients, the parasite might become resistant to the antibiotic. Because little is known about Blastocystis’ metabolic processes, it is not known why metronidazole is effective in some patients and not in others [9].


TMP-SMX is an alternative treatment when metronidazole is not effective. It is not known if TMP-SMX targets the bacteria itself or other bacteria that Blastocystis is dependent on for survival [9].

Although it has a 90%+ success rate in treating Blastocystis in adults, it is less than 40% effective in children. TMP-SMX might only reduce the number of parasites in the body and not completely eradicate it [9].

3) Nitazoxanide

Nitazoxanide is another antiparasitic agent that can help treat infection; it also has no known side effects and has a 97%+ effective rate in children. It kills bacteria that is necessary for Blastocystis growth, but it is only effective in human strains of this pathogen [9].

4) S. boulardii

S. boulardii is a type of yeast that helps kill pathogens; it is 95% effective in children. It affects cellular signaling pathways, regulates the intestinal microbial homeostasis, interferes with the ability of pathogens to colonize, controls local and systemic immune responses, and stabilizes gastrointestinal barrier functions [9].

5) Chinese Medicinal Herbs

Brucea javanica and Coptis Chinensis, Chinese medicinal herbs, are also effective at inhibiting the parasite, but they are not as powerful as antibiotics. If used along with a high-fiber and lactose-free diet, it helps relieve symptoms of infection [9].

How Can You Prevent Infection?

1) Proper Hygiene

Proper sanitation areas with clean water and proper hygiene can reduce your likelihood of being infected [10].

2) Be Careful When Visiting Underdeveloped Countries

Volunteers and travelers to third world countries are very likely to be infected with Blastocystis due to poor sanitary conditions or infected water. The risk of infection is high [11].

Want More Targeted Ways to Combat Inflammation?

If you’re interested in natural and more targeted ways of lowering your inflammation, we at SelfHacked recommend checking out this inflammation wellness report. It gives genetic-based diet, lifestyle and supplement tips that can help reduce inflammation levels. The recommendations are personalized based on your genes.

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About the Author

Helen Quach

BS (Biochemistry)

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