All by-products of animal slaughter are excluded from certain vegetarian types. By-products of slaughter include gelatine (flavourless ingredient that is derived from collagen obtained from various animal body parts), isinglass (a kind of gelatine obtained from fish, especially sturgeon, and used in making jellies) and animal rennet (curdled milk from the stomach of an un-weaned calf, containing rennin and used in curdling milk for cheese).

Most cheese is produced from animal rennet and is consumed by some vegetarians. Chocolates contain gelatine and are also consumed by some vegetarians.

Use of alcohol is prohibited in all vegetarian food preparation.