Blastocystis hominis


Blastocystis hominis infection may or may not result in symptoms. Symptoms revolve around mild to moderate colonic inflammation and systemic Th2-type immune reactivity. Symptoms overlap with various other conditions, so testing is required to identify infection (tests listed below). Following is list of potential symptoms associated with Blastocystis hominis infection:

  • IBS-D
  • Itchy skin (pruritus)
  • Hives (urticaria)
  • Hay fever
  • Food reactions
  • Increased gastrocolic reflex (excessive BMs, esp. in response to food ingestion)​1​
  • Tenesmus (feeling of need to defecate when colon is emptied; associated with diarrhea or IBS)​1​


Although B. hominis is associated with increased symptomatology as outlined above, it doesn’t appear to be overtly pathogenic according to studies. Long HY et. al found that “B. hominis cells were not able to cause cytopathic effects, but significant increases in the release of the cytokines IL-8 and GM-CSF could be observed.”​2​ Varied pathogenicity is associated with different strains of B hominis. Some subtypes of B hominis, particularly type 1, clearly appear to activate the immune system in a pathologic manner. For example, type 1 B. hominis increases pro-inflammatory IL-8 and lowers anti-inflammatory IL-10 in colonic epithelial cells.​3​ Infection is associated with lymphoid hyperplasia, another indicator of immune activation that may explain symptamotology.​1​

Assessment for Blastocystis hominis Infection

  • Physical Symptoms (see symptoms above)
  • Non-specific tests
    • Total serum IgE may be elevated in parasitic infections​4,5​
    • Urinary indican​6​
  • Specific tests
    • Comprehensive digestive stool analysis (microscopy)
    • PCR stool analysis (GI-MAP)

Functional Treatments for Blastocystis hominis


  1. 1.
    de Silva D. Blastocystis hominis Infection: A Real Pathogen? Journal of Pediatric Gastroenterology & Nutrition. 1992;27(2):243.
  2. 2.
    Long H, Handschack A, König W, Ambrosch A. Blastocystis hominis modulates immune responses and cytokine release in colonic epithelial cells. Parasitol Res. 2001;87(12):1029-1030. doi:10.1007/s004360100494
  3. 3.
    YAKOOB J, ABBAS Z, USMAN MW, et al. Cytokine changes in colonic mucosa associated with Blastocystis spp. subtypes 1 and 3 in diarrhoea-predominant irritable bowel syndrome. Parasitology. March 2014:957-969. doi:10.1017/s003118201300173x
  4. 4.
    Ehiaghe AF, Agbonlahor ED, Ifeanyichukwu OM, Kester D, Ehiaghe oy I, Oviasogie FE. Serum immunoglobulin E level of children infected with intestinal parasite in Okada, Nigeria. OJI. 2013:123-126. doi:10.4236/oji.2013.33017
  5. 5.
    Jalalian M. Relationship between Serum IgE and Intestinal Parasites. Iran J Public Health. 2004;33(1):18-21.
  6. 6.
    Jackson J. Urine Indican as an Indicator of Disease. The Journal of Orthomolecular Medicine. 2000;15.

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