Food Sickness is a player survival/consumption mechanic.
While in the Betweenlands, players should not eat the same exact food item too much. Betweenlands food items have a tooltip that changes depending on how intense the food sickness of the item is; for example, a food type that has not been eaten at all, or not too many times, will have the tooltip 'Tastes good'. If they start to eat too much (usually requires having eaten about 22 pieces of the same type of food within a certain amount of time), the tooltip will progress to 'Tastes plain'.
If they continue to eat more (up to 34 pieces), a message will show saying the player is starting to feel sick of eating the item. If they still continue to eat (up to 50 pieces total) the tooltip will further progress to 'Can't eat this anymore' and a message will show saying they should not eat any more of that type of food. They can continue to eat it if they wish, but it will only restore 1 () hunger point/1 () decay point, no matter what the food type is. Eating a different type of food will help to bring the sickness level down on the other food; this requires the player to look for multiple sources of food in order to restore their hunger. An additional message will also display to note that the player is eating a different food and is avoiding the food sickness.
Eating Chiromaw Wings will heavily decrease the Food Sickness level on all other food items, while severely increasing its own sickness level.
There are more than 40 different possible messages that can be used for all of the messages in Food Sickness.