I would also get a Drs note and refer to occupational health for their guidance but gut feel is that one option could be to keep his snack or snacks in an easily accessible (to him) location in a supervisor's office within the production room. These snacks would have to be accounted for at the start and end of his shift and locked away when he's not on shift. He would then have to wash his hands before reverting to production. Also it's important to check his snack does not have any allergens that need to be labelled.
Ideally during this time if he's in an open food area, he could be located to an enclosed food area, like labelling or sleeving depending on your product to limit risks further.
Ultimately though if there's not a work around which fits with food safety, can he be relocated to an office role? If not he may have to be off sick.