Today we’re diving into a common but often misunderstood gut parasite called Blastocystis hominis, or B. hominis for short. We’ll look at the different strains, why some people get sick while others don’t, and how you can effectively treat it. If you've been struggling with digestive issues or unexplained symptoms, this might just be the piece of the puzzle you've been missing.

Blastocystis hominis is a microscopic parasite that lives in the intestines. It’s found all over the world and is one of the most common parasites detected in stool samples.

However, traditionally B. hominis has not been tested for in the U.S., and many doctors are still not testing for it. But more thorough PCR stool panels will usually include testing for B. hominis.

In fact, the conventional medical thinking for the past several decades has been that B. hominis didn’t exist in the U.S., and that even if you had it, it didn’t cause symptoms.

But the reason that it didn’t “exist” is because most doctors weren’t testing for it. And you can’t find what you aren’t looking for. So of course it wasn’t being found.

However, those of us who were testing for it would see it fairly regularly. Which of course leads to the next question, What did I do to treat it?

Most people, when faced with the prospect of being diagnosed with a parasite, will assume that the parasite is the cause of whatever digestive problem that they may have.

However, in the case of B. hominis, it isn’t that simple. Because not all B. hominis are created equal.

Now the reason that doctors weren’t testing for it was because there were studies that concluded that it did not cause symptoms. So why bother testing for something that doesn’t cause symptoms?

But when I dug deeper into the studies on B. hominis, it turned out that there were also studies that found that sometimes it DID cause symptoms. And further studies showed that there were multiple different strains of B. hominis.

Symptoms of B. hominis

What scientists discovered was that some strains of B. hominis DO cause symptoms, and other strains do not. So if you've tested positive for B. hominis, the strain you have can make a big difference in how it affects you.

When B. hominis causes problems, symptoms can vary widely. The most common include:

• Gas and bloating

• Abdominal pain

• Diarrhea or loose stools

• Fatigue

• Brain fog

• Skin issues like rashes or hives

Treating B. Hominis:

Now let’s talk about treatment. This is where things get even more challenging and even controversial.

Because many doctors believe that B. hominis doesn’t cause symptoms, they believe that it doesn’t need to be treated at all. And ironically, sometimes they are correct.

But in my experience, when someone has symptoms and tests positive, we can’t ignore it and treatment can and often does make a huge difference.

1. Prescription Medications

The standard treatment for B. hominis in the U.S. is metronidazole, also known as Flagyl. Metronidazole may be effective, but it is not unusual for B. hominis to be resistant to metronidazole, so it often doesn’t work.

Paramomycin may also be used, but it isn’t available in the U.S.

The most successful drug for treating B. hominis is called nitazoxanide, which is also known as Alinia. It isn’t perfect, but in my experience it works much better than metronidazole.

And sometimes a triple therapy combining multiple medications is more effective, especially in resistant cases.

2. Herbal Antimicrobials

For those preferring a natural route, herbal protocols often include ingredients like the following:

• Berberine

• Oregano oil

• Garlic

• Black walnut

• Neem

These can be surprisingly effective, and we’ve used these many, many times at the IBS Treatment Center. These also help support gut health and the microbiome, which is often disrupted by B. hominis.

3. Support the Terrain

Ultimately, treating B. hominis isn’t just about killing the bug. It’s about restoring a healthy gut environment. This includes:

• Supporting digestion and detox pathways

• Rebalancing the microbiome

• Healing the gut lining

• Addressing any food sensitivities and inflammation

Many people find that once their gut terrain is healthier, they do much, much better.

So yes, B. hominis can be tricky. But it’s also manageable with the right approach. If you’re dealing with persistent GI issues or mysterious symptoms, don’t overlook this parasite—especially if standard treatments haven’t worked.

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