Published March 7 2016
Blastocystis hominis is an enteric parasite that can inhabit the gastrointestinal tract of humans, as well as many animals. There is some controversy over whether this parasite is commensal, and thus isn’t harmful, or if it is pathogenic. The more recent research seems to point towards Blastocystis hominis as being a pathogenic parasite that should be eradicated. And there is some evidence that it can be a potential trigger for Hashimoto’s Thyroiditis.
Before discussing some of the research, it probably is a good idea to discuss how to tell if someone has Blastocystis hominis. Well, the most frequent symptoms associated with Blastocystis hominis include abdominal pain and diarrhea, and some other symptoms include anorexia, fever, anal itching, and nausea (1) . However, not everyone with Blastocystis hominis experiences symptoms. In addition, the presence of some of these symptoms isn’t specific to Blastocystis hominis, as these symptoms can indicate a different type of parasitic infection.
And so in order to confirm if someone has Blastocystis hominis it is necessary to do a stool test. This can be done at a conventional lab, although it might be best to get it done through a “professional” lab such as Genova Diagnostics, Doctor’s Data, or BioHealth. And there are a few reasons for this. First of all, their technicians do a lot of these tests, and so the chances of a false result due to lab error is less when using one of these labs. Second, all three of these companies give the option of collecting more than one stool sample. Collecting a stool sample on three or four different days decreases the chance of having a false negative result. Keep in mind that there are other professional labs besides the three I mentioned, but these are the ones I’m most familiar with. Of course if you have health insurance that will cover a one sample stool test at a conventional lab you can start by doing this, but just keep in mind that a negative result won’t necessarily rule out Blastocystis hominis.
Is There A Relationship Between Blastocystis Hominis And Hashimoto’s?
Before talking specifically about Blastocystis hominis and Hashimoto’s Thyroiditis, I’d like to briefly discuss how this parasite affects the immune system. Blastocystis hominis appears to increase proinflammatory cytokines, including interleukin 1β (IL-1β), IL-6, and tumor necrosis factor alpha (2) . These proinflammatory cytokines are linked to autoimmune diseases, including Hashimoto’s Thyroiditis. In addition, Blastocystis hominis can increase intestinal permeability (3)  (4)  (5) . In other words, this parasite can cause a leaky gut, which is a factor in many, if not all autoimmune conditions.
There is a case report involving a 49-year old man with chronic urticaria and Hashimoto’s thyroiditis, and this showed that eradicating Blastocystis hominis with Metronidazole got rid of the urticaria, and normalized the thyroid hormones while decreasing the thyroid antibodies (6) . Of course we need to keep in mind that this is just a single case study, although I have worked with a few Hashimoto’s patients who tested positive for Blastocystis hominis and went into remission upon eradication. Many reading this are familiar with Dr. Izabella Wentz, who is a pharmacist that was diagnosed with Hashimoto’s Thyroiditis. In an article  written by her she mentioned the following: “I’ve found that eradicating a Blastocystis infection in a person with Hashimoto’s often leads to a remission of Hashimoto’s, with an improvement in symptoms, a reduction in food sensitivities and a reduction in thyroid antibodies”.
It’s also worth mentioning that research shows an increased risk of infection with Blastocystis hominis when stress is present (7) . The reason for this is because Blastocystis hominis is opportunistic in immunocompromised patients, and stress can suppress the immune system and make someone more susceptible to such an infection.
Should Blastocystis Hominis Be Eradicated?
As I mentioned in the opening paragraph, some sources consider this to be a commensal organism. One older study concluded that Blastocystis hominis “is a commensal germ of the intestinal tract and does not usually require prescription of an antibiotic.” (8)  Another study showed that 8% of stool samples harbored blastocystis, but also mentioned that it was a commensal organism (9) .
However, eventually it was suspected that Blastocystis hominis might be a possible cause of intestinal diseases (10)  (11) . One of these studies concludes that Blastocystis hominis is a potential pathogen that may or may not require drug therapy depending on the overall clinical circumstances, the severity of symptoms, and the presence of other pathogenic organisms (11) . Another more recent study mentioned how this species isn’t commensal, and is now being regarded as a parasitic organism (12) .
If Blastocystis hominis is indeed pathogenic, then it would make sense to eradicate it if tested positive on a stool test, right? Well, since it might be a potential trigger for Hashimoto’s Thyroiditis, if someone with this condition tests positive for this parasite then it probably is a good idea to eradicate it. Similarly, if someone doesn’t have Hashimoto’s but has gastrointestinal symptoms, then it also would be wise to kill off this parasite. On the other hand, some recommend that people who test positive for Blastocystis hominis but are asymptomatic shouldn’t receive treatment (13) . However, if this is a potential trigger for autoimmunity, it might make sense to eradicate it even if symptoms aren’t present.
How To Eradicate Blastocystis Hominis
The main conventional treatment method for Blastocystis hominis involves giving the drug Metronidazole, also known as Flagyl. This is an antibiotic, and in some cases Blastocystis hominis is resistant to this drug (14)  (15) . Other agents which can also be used to eradicate Blastocystis hominis include trimethoprim-sulfamethoxazole, paromomycin, and furazolidone (15) . The downside of using these drugs is that side effects are more common when compared to using natural agents, and they can also harm some of the good flora. The advantage of using medication is that assuming it works, it almost always works much faster than taking natural agents.
Speaking of taking a natural approach, there is some evidence that garlic and ginger can significantly help with the eradication of Blastocystis hominis, while onion and turmeric treatments weren’t too effective (16) . Wormwood and clove have shown evidence to be effective against parasitic infections (17)  (18)  (19) , although in the literature there is no evidence that specifically show that these eradicate Blastocystis hominis. But I like using these herbs for all parasitic infections, along with black walnut, and there is also evidence that oregano oil can help with the eradication of Blastocystis hominis (20) . This study used 600mg of oregano oil daily for six weeks, and I would recommend dividing the doses into 200 mg three times per day.
There is some evidence that Saccharomyces boulardii can help to eradicate Blastocystis hominis. One study looked at the clinical efficacy of S. boulardii or Metronidazole in symptomatic children infected with Blastocystis hominis (21) . This involved taking 250mg of S. boulardii twice per day, and at the end of the first month 94.4% of those who took S. boulardii were cured, compared to 73.3% of those who took the Metronidazole (21) . Another study involved two groups, both who were treated with Metronidazole, but S. boulardii was taken by one of the groups for 7 days, and on day 5 the amebic cysts disappeared in all children who were also taking S. boulardii, while in the other group, amebic cysts were still present in 6 children (out of 25). (22) .
In summary, Blastocystis hominis was once thought to be a commensal organism, but it is now considered to be a pathogenic parasite. In order to confirm if someone has Blastocystis hominis one must do a stool panel, preferably collecting a stool sample on multiple days. There is evidence that Blastocystis hominis can increase proinflammatory cytokines and increase intestinal permeability, and both of these are factors with autoimmune conditions such as Hashimoto’s Thyroiditis. Although drugs such as Metronidazole can help to eradicate Blastocystis hominis, some natural agents which have been shown to eradicate Blastocystis hominis include garlic, ginger, oregano oil, and saccharomyces boulardii.