Cross-contamination is one of the biggest factors related to foodborne illness. It is vital that proper precautions are taken to prevent foodborne illnesses in your operation because the consequences could be costly (read more about these consequences in our Crash Course on Food Safety). One such precaution is learning more about what cross-contamination is, how it occurs, and how to prevent it. 

What is Cross-Contamination?

Cross-contamination occurs when pathogens – microorganisms like bacteria that can cause disease – are transferred from one food product or surface to another, potentially resulting in foodborne illness. There are several ways this could happen: 

  1. Contaminated ingredients are added to food that receives no additional cooking. 
  2. Ready-to-eat food comes into contact with a contaminated surface. 
  3. A contaminated food touches, or drips fluid, onto a cooked or ready-to-eat food. 
  4. A food handler touches a contaminated food and then touches a ready-to-eat food.
  5. A contaminated wiping cloth touches food-contact surface. 

Pathogens can transfer easily, spread from food or unwashed hands to prep areas, equipment, utensils or other food. This can occur throughout any point of the flow of food – the path that food takes through your operation, from receiving to storing, prepping, cooking, holding, serving, etc. Knowing how and where it can happen is half the battle. Master that, and it becomes much easier to prevent.

Types of Cross-Contamination

There are three broad types of contaminants:

Biological Contamination

Biological contamination occurs when harmful microorganisms, or pathogens, are consumed. There are four types of pathogens that can contaminate food and cause foodborne illness: bacteria, viruses, parasites, and fungi (mold and yeast). The FDA reports more than 40 kinds that can occur in food and cause illness. The Big Six – dubbed because they are highly contagious and can cause severe illness – include: 

  1. Shigella – often transferred from flies
  2. Salmonella Typhi – lives only in humans, transferred from person to person 
  3. Nontyphoidal Salmonella – lives in animals, transferred from poultry, eggs, meat, dairy products, and produce 
  4. Shiga toxin-producing Escherichia coli (E. Coli) – found in ground beef and contaminated produce 
  5. Hepatitis A 
  6. Norovirus 

If a food handler has been diagnosed with any one of these six, they must be excluded from the operation until symptoms disappear and a doctor says they can come back. In order to prevent these, it is essential to know how each of the four pathogen types occur. 


Bacteria requires six conditions to grow: food, acidity, temperature, time, oxygen and moisture (FATTOM). To prevent bacteria growth, the best course of action is to control time and temperature, always doing your best to ensure that food mandating time and temperature control is kept out of the temperature danger zone (between 41°F and 135°F). 


Viruses need a living host to survive, thus why they are carried and transmitted by humans and animals. People can contract a virus from food, water or contaminated surfaces. Unlike bacteria and parasite, viruses cannot be destroyed by cooking food to minimum internal temperatures. The best way to prevent a virus is by practicing good personal hygiene and mandating staff stay home when they’re ill. 


Parasites are commonly associated with seafood, wild game, and food processed with contaminated water, like produce. They require a host to thrive. To prevent, always ensure your food products are purchased from an approved, reputable supplier and that cooked food meet the required minimum internal temperatures. 


Many biological toxins are associated with certain plants, mushrooms, and seafood. Histamine is a prominent toxin produced by pathogens, occurring when fish is time-temperature abused. It can often be found in tuna, mackerel, mahi-mahi, and bonito.  

Ciguatera is another common toxin that is transferred when a large fish eats a smaller fish and then passed onto humans if appropriate preventative measures are neglected. This is often observed in barracuda, snapper, grouper, and amberjack. 

Onset times for symptoms of biological contamination vary; however, with toxins, symptoms typically occur within minutes of consumption. The most commonly observed symptoms of biological contamination include nausea and upset stomach. Though these may be present in contamination caused by toxins, one key distinguisher is the onset of neurological symptoms. In addition to nausea, many experience hot and cold sensations, tingling in the extremities, flushing of the face, difficulty breathing, heart palpitations and hives. 

The most important way to prevent toxins in your foodservice is ensuring all plant-based or seafood products are purchased from approved suppliers, and adequately controlling time and temperature when handling raw fish. 

Chemical Contamination

If not correctly utilized, everyday chemicals like cleaners, sanitizers, and polishers can contaminate food and cause illness. Ensure that chemicals are approved for use in a foodservice operation and purchased from approved suppliers. Store away from prep areas, food storage areas, and service areas, and separate from food and food-contact surfaces with proper spacing and partitions. Never store chemicals above food or food-contact surfaces, and always use them only for their intended use, following the manufacturer’s directions. Also, be sure to handle food only with equipment and utensils approved for foodservice. All chemicals should be clearly labeled.

Physical Contamination 

Physical contamination occurs when physical objects find their way into foods. These could include dirt, hair, bandages, metal shavings, glass, jewelry, etc. Natural objects, such as fish bones, are also considered physical contaminants. These could cause mild to fatal injuries such as cuts, dental damage, and choking. To help prevent this, carefully inspect all food you receive, and take steps to make sure food handlers are aware of their surroundings. Jewelry should be removed and hair nets donned before handling food.  

How to Prevent Cross-Contamination During the Flow of Food

The flow of food refers to the path food takes throughout the operation, from the initial purchasing to receiving, storing, preparation, cooking, holding, cooling, reheating, and serving. To effectively prevent cross-contamination, proactive measures must be taken throughout each step of this path. There are programs and resources available to assist operators in establishing the level of vigilance required to prevent cross-contamination and protect guests, staff, and your business. See our article on developing a HACCP plan to learn more about these available resources.

Several steps should be implemented and adhered to strictly to reduce the risk of cross-contamination when handling food. These include:

1. Use separate equipment for raw and ready-to-eat food

While there is no substitute for thorough cleaning and sanitizing equipment and supplies after every use, color coding your food prep supplies is a great way to reduce the risk of cross-contamination. Separate types of food mandate the use of different equipment and utensils. Colored cutting boards and utensil handles can help keep everything separate and organized while keeping awareness top of mind. The color tells the food handler what type of food should be prepped. Traditionally, green has been used to indicate use for produce, yellow for raw poultry, blue for cooked food, white for dairy products, brown for seafood, and red for raw meat.  

Color-coded knives and cut-resistant gloves can be coordinated with your cutting boards to ensure certain colors are only used for particular food items.

Green, color-coded cutting board for produce

A green cutting board is traditionally used for prepping fresh produce.

Yellow, color-coded cutting board for poultry

Use a yellow cutting board and utensils for handling raw poultry.

Blue, color-coded cutting board for cooked food

Use blue cutting boards and supplies for cooked foods.

White color-coded cutting board for dairy products

White cutting boards and supplies are ideal for dairy products.

Brown color-coded cutting board for use with seafood

Brown cutting boards and supplies are used when dealing with seafood.

Red color-coded cutting board for raw meat

Traditionally, red cutting boards and supplies have been used to indicate use for raw meat.

Purple color-coded cutting board for allergen special orders

As food allergies become increasingly more common, many have taken to using purple color-coded supplies to prep allergen special orders.

2. Properly clean and sanitize before and after tasks

To ensure pathogens are properly killed and to reduce the risk of being transferred to ready-to-eat foods, all work surfaces, equipment, and utensils need to be cleaned and sanitized before and after each task. It’s not enough to simply rinse.  

And, as always, hands should be washed thoroughly as well to ensure there’s no trace of contaminants before starting on the next task.

See all cleaning supplies and hand washing supplies.

3. Prep raw and ready-to-eat-food at separate times

If you need to use the same prep table to prepare different types of food, especially raw foods that need to be cooked to minimum internal temperatures, do so at different times than ready-to-eat food. You can reduce the potential for cross-contamination by prepping ready-to-eat foods before raw foods. 

4. Buy food that’s already been prepared 

For example, bagged chopped lettuce or precooked chicken. Improper handling of food is a prominent contributor to cross-contamination, so it stands to reason that purchasing foods that do not require handling dramatically reduces risk. 

Remember, proactivity is key. You can achieve this by incorporating active managerial control in your operation. When it comes to food safety, there is no shortage of vital practices. 

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