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Food allergies and cross-contamination

By Jane Harrison, R.D., Staff Nutritionist, myOptumHealth

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Lisa broke out in hives after eating salad from the cafeteria salad bar. Being allergic to soy, she was careful to avoid the soy items. But she didn’t know that the spoon she used for the cucumbers had been used to scoop out tofu by someone else.

Andy, allergic to wheat, ordered plain grilled chicken at a restaurant. After a few bites, he started to have an asthma attack. Turns out his chicken was cooked on the same grill as the wheat-containing marinated chicken and steak.

Joan started to have trouble breathing after she ate what she thought was a nut-free candy bar. She didn’t know that the manufacturing company (which also makes candy bars with nuts) had not cleaned their machinery properly between shifts.

What is cross-contamination?

Cross-contamination occurs when an unsafe food comes into contact with a safe food and taints it. The contact can be direct or from sharing a surface. It can happen at home, in restaurants or during manufacturing.

Only a tiny amount of allergen is needed to trigger an allergic reaction. So, cross-contamination is an important concern for people with serious allergies. Simply avoiding the food source is not always enough. If you have a severe allergy to certain foods, you must be extra cautious at home and when you are out.

Follow these tips to avoid cross-contamination:

Be wary of packaged foods. The FDA requires manufacturers to mention whether their factory uses common allergens (wheat, peanuts, tree nuts, milk, soy, eggs, fish and shellfish). But they don’t have to report whether the plant makes other items containing these allergens (which makes cross-contamination possible). If it’s not clear from the label what’s in a product, your best bet is to call or e-mail customer service and ask directly before you eat the product.

Keep allergens away from safe foods. If you must keep allergens in your home, you can lower your chances of cross-contamination by:

  • Keeping them away from food preparation and serving areas
  • Reserving special prep areas and utensils for allergens
  • Thoroughly cleaning all food surfaces that have touched allergens as soon as you’re finished using them
  • Using disposable plates and plastic utensils if you serve allergens on only rare occasions

Be watchful in restaurants. Cross-contamination can occur while food is being cooked or from sharing cutting boards.

  • Ask for your dish to be grilled in a separate pan if possible.
  • Try to avoid anything fried in oil in which a food you are allergic to has been fried. The frying oil may be tainted.
  • If you receive an incorrect order (such as walnuts on your pancakes and you are allergic to tree nuts), send it back and ask for a new plate. Scraping off the walnuts does not ensure the dish will be free of the allergen.

 Be cautious at salad bars. Cross-contamination is especially common at salad bars.

  • Spoons are often moved from one container to another.
  • If you are severely allergic to an item on a salad bar, you should generally avoid eating from that salad bar.

There are no medications to cure food allergies, and allergy shots have not been proven to help. To be absolutely safe, strict avoidance of the allergen is the only way to prevent a reaction.

View the original Food allergies and cross-contamination article on myOptumHealth.com 


  • United States Department of Agriculture. National Agriculture Library. Food allergies and sensitivities.
  • Food and Drug Administration. Food labels identify allergens more clearly.



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