When cold season or allergy season hit, many people reach for their neti pot to flush out clogged nasal passages, but now the U.S. Food and Drug Administration (FDA) is warning consumers that using tap water could cause potentially serious infections, including a rare brain-eating amoeba.

Neti pots, which are little teapots with long spouts, are frequently used to treat symptoms of the common cold or moisten nasal passages. However, the FDA urges proper use to decrease the likelihood of infection.

In a Jan. 24 update of its article on neti pots, the FDA said it is important to use distilled, sterile or previously boiled water to flush out the nose.

“Tap water isn’t safe for use as a nasal rinse because it’s not adequately filtered or treated,” the FDA said on its site. “Some tap water contains low levels of organisms — such as bacteria and protozoa, including amoebas — that may be safe to swallow because stomach acid kills them. But in your nose, these organisms can stay alive in nasal passages and cause potentially serious infections.”

In very rare cases, a person can also contract Naegleria fowleri. Commonly known as the brain-eating amoeba, Naegleria fowleri can enter through the nose and migrate to the brain. In 2011, two adults died in Louisiana hospitals after using contaminated tap water with neti pots. The amoeba kills 97 percent of people it infects.

The FDA recommends using tap water that’s been boiled for three to five minutes and then cooled or store-bought water that’s been labeled distilled or sterile. Water passed through certain filters that trap infectious organisms is also fine.

While rinsing sinuses can remove dust and pollen, as well as help loosen thick mucus, the FDA encourages consumers to follow directions carefully and wash the device thoroughly. The agency also says to consult a doctor and report unexpected symptoms.

“Whether for a child or adult, talk to your health care provider to determine whether nasal rinsing will be safe or effective for your condition,” the FDA says. “If symptoms are not relieved or worsen after nasal rinsing, then return to your health care provider, especially if you have fever, nosebleeds or headaches while using the nasal rinse.”