A “mass intoxication event” took place at Famous Yeti’s Pizza in Wisconsin in October 2024, according to a paper recently published in a US health journal.

Staff at the pizzeria ran out of cooking oil and decided to borrow oil from a shared kitchen in the same building, unaware that it was infused with tetrahydrocannabinol (THC), the psychoactive component in cannabis.

Cannabis is illegal for recreational use in Wisconsin, but edible cannabis products with small amounts of hemp-derived THC are legal.

Seven people went to hospital with symptoms including “dizziness, sleepiness and anxiety” and were found to have eaten at the same restaurant.

Health officials subsequently identified 85 customers who ate its pizza, garlic bread, cheese bread or sandwiches and experienced similar symptoms.

“Co-location of food establishments with businesses that make THC-infused products increases the risk that a THC-containing ingredient might be added to food, either intentionally or unintentionally,” the new paper in Morbidity and Mortality Weekly Report (MMWR) notes.

“Health care providers, public health professionals, and emergency responders should consider THC intoxication in persons with sudden onset of symptoms such as dizziness, sleepiness, anxiety, altered reality perception, increased heart rate, nausea, or other symptoms of THC ingestion.

“Regulations regarding practices such as standard, clear labelling and locked storage for ingredients containing THC, might decrease the risk for unintentional THC exposure at licensed food businesses.”