THC in the Pizza Dough: 85 People Intoxicated by a Wisconsin Restaurant's Food, 2024

Tetrahydrocannabinol (THC) is the psychoactive substance in Cannabis sativa plants — including hemp, which has less of it — and it's turning up in more and more consumer products. In October 2024, it turned up where no one expected it: in the pizza dough at a restaurant in Dane County, Wisconsin.

How it was discovered

On October 24, local emergency medical services told Public Health Madison & Dane County (PHMDC) that since October 22 they had taken seven people to a hospital in Stoughton with dizziness, sleepiness and anxiety — all of whom had recently eaten food from the same restaurant. Carbon monoxide tests at two homes and the restaurant were negative. One patient, who had eaten pizza on October 23, then called PHMDC: they had tested positive for THC without knowingly taking any.

What went wrong

• The restaurant shared a building with a cooperative (shared) kitchen, where a state-licensed vendor made edible products with hemp-derived Δ9-THC, infusing cooking oil on site.
• On October 22, the restaurant ran out of cooking oil and used oil from the shared kitchen to make dough served October 22–24. The owner thought it was plain canola oil.
• Oil from a large labeled container in the same area tested positive for THC.
• Police found the contamination unintentional; no charges were filed. The restaurant closed on October 24 and reopened October 26 after cleaning and sanitizing.

Containers of hemp-derived THC-infused cooking oil found in the same area as the oil used for the dough. Image from CDC's report

Who got sick

PHMDC posted an online questionnaire and publicized it by press release and social media. Of 208 responses, 101 were thrown out — incomplete, from people who hadn't eaten there, or joke entries using fictional characters or marijuana-themed names — leaving 107.

85 people met the case definition: they ate pizza, garlic bread, cheese bread or a grinder (submarine sandwich) from the restaurant during October 22–24 and developed THC symptoms within 5 hours.

Symptoms included dizziness, sleepiness, anxiety, memory or time distortion, fast heartbeat, nausea, paranoia, panic attacks, higher blood pressure, vomiting and hallucinations. The youngest, aged 1, had dizziness. Another eight ill people were named by others but didn't respond.

PHMDC warned the public not to eat leftover pizza from those dates, later adding grinders and bread.

Timeline of the outbreak. Image from CDC's report

Lessons

• Consider THC intoxication when people suddenly develop dizziness, sleepiness, anxiety, altered perception, a racing heart or nausea — and be alert to mass poisonings through food.
• The Food and Drug Administration has not found any use of THC or other cannabinoids in food to be safe and lawful under federal food law, yet such products are sold in cannabis and hemp markets. Sharing kitchens with THC product makers raises the risk of contamination.
• Clear, standard labeling and locked storage of THC ingredients could reduce accidental exposure at licensed food businesses.

Limits: no leftover food was tested, the oil wasn't tested quantitatively, and there was no case-control study.

Sources

Based on Amanda Kita-Yarbro, Stefanie Moccero, Katie Brobston and others, "Tetrahydrocannabinol Intoxication from Food at a Restaurant — Wisconsin, October 2024," MMWR, volume 74, Centers for Disease Control and Prevention; a work of the United States government in the public domain. The report describes four children under 13 as aged 3–8 while also reporting a 1-year-old case, so that breakdown is not given here; the descriptions of its two figures are swapped in the source and corrected here.