There are many foods that one wouldn't think contain animal products but do. Foods such as gelatin, pie crusts made with lard, and vegetable soups made with chicken broth are all no no's for vegans and for strict vegetarians. So keep in mind if you're preparing a special meal for a vegetarian or vegan that they can't eat that Strawberry Gelatin Salad, Split Pea Soup flavored with ham hocks or Aunt Zelda's Famous Green Beans with Onions sauteed in bacon grease. A vegan won't be able to eat a slice of traditional pumpkin pie or a piece of chocolate cake made with eggs. Cheeses, especially hard cheeses like Parmesan, Romano and Cheddar, usually contain rennet.
Rennet is meat by-product.
When purchasing cheeses look for ones labeled Kosher, rennetless or rennet-free. Many cheese spreads contain gelatin, which is another meat by-product. To ensure that your cheeses are okay for vegetarians be sure to read the labels when purchasing. Just because a person chooses not eat meat products or animal products for health or other reasons doesn't mean they don't eat well. In fact vegetarians and vegans eat very well.