On a Reddit thread discussing what not to order at fast food restaurants, purported Wendy's employee u/sofiercexstar shared some words of caution about the chain's Frosty.
According to the Reddit user, many employees fail to clean the Frosty machine correctly. While unclean soft serve machines are fairly common, they can still be dangerous.
Unclean machines can be a breeding ground for listeria bacteria, which is the third leading cause of foodborne illness-related death in the U.S., according to the CDC.
In addition, leftovers from the Frosty machine are poured into buckets at night, left in the fridge (sometimes uncovered,) and put back into the machine the next morning.
How the Frosty mixture is handled can also be a concern, as mixtures have a very narrow safe temperature range. If they're mishandled, harmful bacteria can flourish.