Our discussion today revolves around a microscopic parasite called Blastocystis hominis, a case of hives and Hashimoto’s disease!

The case report was published in 2015 in The Journal of Infection in Developing Countries.  The report was entitled, “Eradication of Blastocystis hominis prevents the development of symptomatic Hashimoto’s thyroiditis: a case report.  The case involved a singular subject who was suffering from chronic urticaria (hives), angioedema (skin swelling) and overly soft stools who also showed signs of Hashimoto’s disease.

But before we delve into more details, let me provide you with some basic background information.

Background on Blastocystis Hominis

Blastocystis hominis is the most common protozoan parasite in humans with incidence between 5-75% depending on the country's level of development.  In the past, it had been considered as a non-pathogenic parasite. However, studies by the research teams of Katsarou-Katsari, et al. (2008), Valsecchi et al. (2004) and Vogelberg et al. (2010) showed that Blastocystis hominis infection is associated with chronic urticaria.

What is urticaria?

In general, urticaria is a very common skin disorder that can have immune, non-immune or idiopathic causes.  It appears as swollen, pale red bumps or plaques.

When the skin lesions appear within a six-week period, the patient would be described as having a case of acute urticaria.  Anything longer than six weeks, however, is clinically defined as chronic urticaria.

You may be wondering at this point what a parasite and a skin condition have to do with Hashimoto’s disease.

Existing research has revealed that chronic urticaria and the presence of anti-thyroid antibodies, or autoimmune thyroid disease, have some kind of association with reported prevalence from 12-29%.

How does the parasite Blastocystis Hominis trigger Hashimoto's disease?

A study conducted in 2004 by Pasqui et al. and a clinical review published in