Biological food contaminants such as bacteria, viruses and parasites are the most common food hazard. Chemical hazards or toxins will also contaminant food. Food itself can also be a contaminant, causing allergic reactions. The major food allergens are milk, eggs, fish, crustacean, shellfish, wheat, soy, peanuts and nuts.

Food contamination can be prevented in a number of ways. Washing hands thoroughly with soap and water prevents the cross contamination of food by touch. Washing kitchen utensils, equipment and dishes with boiling water or in a dish washer every time they are used; reduces the risk of residual cross contamination. And, when preparing or finishing food to be set aside, ensure that it is covered at all times. 

High risk foods are those already processed which require zero or minimal cooking before consumption. These are more susceptible to bacteria (and bacterial growth) and other micro organisms because the food is already cooked (further heating can't reduce any associated risk as it isn't required).

They include:

• Cooked meat and fish
• Shellfish
• Dairy products like milk, cream, cheese and soya milk
• Cooked rice
• Gravy, stock, sauces and soups