Don’t use unsterilized tap water to rinse your sinuses. It may carry brain-eating amoebas

Two new studies document rare infections from using the wrong liquid for nasal rinses

A single silver tap protrudes from a crumbling beige tiled wall. There is a stream of water running from the tap. A circular inset with a triangle pointing to the water has an illustration of one pink blobby amoeba with at least five knobby protrusions. Part of another pink amoeba is visible in the left side of the circle.

Brain-eating amoebas like Naegleria fowleri (illustration inset, right) may lurk in tap water (photo). Using unsterilized tap water for nasal rinses for health or religious reasons could, in rare cases, give people deadly brain infections.


Nasal rinses can relieve sinus congestion. But using the wrong liquid can, in rare cases, give people infections with deadly brain-eating amoebas.

Washing the sinuses with unsterilized tap water can expose people to Acanthamoeba and Naegleria fowleri, amoebas commonly found in lakes, rivers and other bodies of water, but which can also live in tap water. The single-celled organisms can cause skin diseases, eye or lung infections and fatal brain infections (SN: 7/20/15).

That practice is the likely source of rare Acanthamoeba infections in 10 people in the United States, most of which occurred in the past decade, researchers from the U.S. Centers for Disease Control and Prevention report March 12 in Emerging Infectious Diseases. Three died.  

And in Pakistan, a 22-year-old man who rinsed his sinuses with tap water as a religious ritual was infected with N. fowleri. Brain infections with those amoeba are almost always fatal, but the man lived thanks to early diagnosis and aggressive treatment, doctors from PNS Shifa Hospital and Aga Khan University in Karachi report March 13 in a separate study in Emerging Infectious Diseases. He is one of only eight known survivors of N. fowleri brain infections worldwide.

Such infections are rare. Acanthamoeba affects only three to 12 people each year in the United States. But about 82 percent of the infections are fatal. About three N. fowleri infections happen in the United States each year (SN: 9/18/20).

All 10 of the people in the CDC study had one or more conditions that weakened their immune systems, including cancer or HIV/AIDS. One person got infected after two weeks of rinsing, while others had been doing nasal washes for years. Four reported using unsterilized tap water and one used sterile water, but then immersed their rinsing device in unsterilized tap water. The type of water used in the other cases wasn’t known.

While rare, these cases illustrate that using unsterilized tap water could leave some people vulnerable to infection with amoebas, the researchers say. People should use distilled, sterile or filtered water or tap water that has been boiled for five minutes and then cooled in their sinus rinses.

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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