People will try just about anything to combat a bad case of the sniffles. Whether it’s from a cold or allergies, a runny or stuffy nose is incredibly annoying, and one of the at-home treatments that’s gained traction in recent years is the use of a “neti pot” to run water through the sinuses. Doing so can provide at least temporary relief, but doctors now believe that a Seattle woman’s fatal brain condition may have been linked to her use of the product.

In a paper published in the International Journal of Infectious Diseases, the 69-year-old woman’s case is explained in detail. She performed sinus irrigation to help with a sinus infection, but used tap water to do so. That water is believed to have contained an amoeba that ultimately took her life many months later.

The effectiveness of sinus irrigation is debatable, but it’s important to note that manufacturers of the small pots used to send water through the nose always recommend that only sterile water be used. Untreated tap water would be a big no-no, and in this case the amoeba Balamuthia mandrillaris is believed to have been present in the water.

Once it has infected a person, the amoeba can cause an incredibly serious and almost universally fatal condition known as “granulomateous amoebic encephalitis,” or GAE. That’s exactly what happened to the unnamed elderly Seattle woman.

Prior to her passing, the woman experienced a seizure as well as a sensitive spot on her nose. The symptoms confused hospital staff, and a CT pointed to a possible tumor. What the CT actually showed was a lesion on her brain and upon opening her skull a surgeon discovered the amoeba infection. By that point there was little modern medicine could do to save her.

It goes without saying, but if you regularly use neti pots or similar sinus irrigation devices, always make sure you’re using sterile water and not whatever is coming out of your tap.