Blastocystis is one of the most common parasites I see in my practice—which may in part be because it’s one of those that does show up in stool cultures if it’s present. (Many cultures for larger organisms are very hit-or-miss.)
Like many common viruses and bacteria, blastocystis may or may not be pathogenic: that is, it can be found in those with no gut symptoms. Whether or not it leads to symptoms seems to be a function of the individual’s immune system and the specific strain.
Most of the time, though, it presents with symptoms of IBS (Irritable Bowel Syndrome), including gas, bloating, cramping, diarrhea, and nausea, as well as the more systemic symptoms that go along with poor digestion, like fatigue.
But these are all very non-specific symptoms which can be caused by a number of different things. I’m most concerned today with some of its more characteristic symptoms: specifically, the development of new and ever-increasing food reactions, and chronic hives.
Leaky Gut, Blastocystis, and Autoimmunity
Your secretory IgA is the immune system of the gut, helping to maintain the integrity of the small intestine barrier. Blastocystis degrades IgA, which may be part of the reason why it is associated with increased intestinal permeability, or “leaky gut syndrome,” leading to production of IgG antibodies against frequently consumed foods.
Blastocystis has also been associated with Hashimoto’s Thyroiditis, most likely for the same reason: about 80% of the immune system is in the gut, and if the gut barrier is disrupted, autoimmunity can easily follow.
Hives and Itching with Blastocystis
Hives are more often an IgE (hypersensitivity) response, with a sudden release of large amounts of histamine. It is speculated that blastocystis triggers hives via inducing an IgE response.
Testing and Treatment
A comprehensive stool culture and parasitology is required for diagnosis.
Treatment is generally metronidazole, but there are now some strains that are resistant.