The US Food and Drug Administration on Monday advised consumers to avoid nine types of hand sanitizers that may contain methanol, a toxic alcohol that can cause blindness if swallowed and systemic effects if absorbed through the skin.

All nine hand sanitizers are made by Eskbiochem SA de CV in Mexico. The agency said in its advisory that it discovered methanol while testing two of the company’s products. One, called Lavar Gel, was 81-percent methanol—and no ethanol, a safe alcohol meant to be used in hand sanitizers. Another, CleanCare No Germ, was 28-percent methanol.

“Methanol is not an acceptable ingredient for hand sanitizers,” the FDA wrote. With use of hand sanitizers at a high amid the COVID-19 pandemic, the agency advised that anyone who has used the methanol-containing products “seek immediate treatment, which is critical for potential reversal of toxic effects of methanol poisoning.”

Toxicity

Methanol, the simplest alcohol, is extremely poisonous and can cause harm if swallowed, inhaled, or absorbed through the skin. It’s often associated with incorrectly distilled liquor. Drinking as little as 30 milliliters—1 ounce or 2 tablespoons—can be fatal to children. Smaller doses can cause permanent blindness.

Inside the body, methanol is metabolized to formaldehyde, then to formic acid. This can lead to metabolic acidosis, a dangerous buildup of acid in the body that can cause organ damage. Formic acid can also accumulate in the optic nerve, causing severe damage that can lead to permanent blindness.

According to safety documents, symptoms of poisoning by ingestion can manifest as gastrointestinal irritation—with nausea, vomiting, and diarrhea—and central nervous system depression, causing headache, dizziness, drowsiness, nausea, and an intoxicated feeling. This can progress to rapid breathing, slowed heart rate, kidney dysfunction, loss of consciousness, coma, and death.