Clostridium botulinum can grow in low-oxygen environments and produce botulinum toxin. FoodSafety.gov links foodborne botulism to improperly canned or preserved foods.
Botulism is a medical emergency. FoodSafety.gov lists symptoms such as muscle weakness, vision problems, and difficulty swallowing in older children and adults.
Follow safe home-canning guidance and do not feed honey to infants under 12 months.