Contaminação cruzada - Fidu | Alimentos Inclusivos

Cross contamination

What is cross-contamination and why is it so important for allergy sufferers and celiacs to avoid it?

In both food allergy and celiac disease, the only way to treat and prevent adverse reactions is to exclude from the diet all foods that cause the reaction (the allergen in question, in the case of allergy, and gluten, in the case of celiac disease). and also foods that may contain the allergen/gluten in their composition intentionally or accidentally. (1)

Cross-contamination represents one of the biggest sources of hidden allergens in food, making it difficult to comply with food exclusion, being responsible for about 21% of allergic reactions. (2.3)


What is cross contamination?

Cross-contamination is a phenomenon that occurs when a safe food contains a small amount of allergen by contact with another food, utensil or contaminated surface, thus becoming dangerous for the individual with food allergy.
Even in very small amounts (traces), the presence of allergens in people with high sensitivity can be enough to cause a severe reaction. (1.4)

How does cross contamination occur?

Cross-contamination can occur through direct contact, for example, when one food is placed on top of another or two foods are placed on the same plate; or indirect, when contamination occurs through hands, containers, utensils, equipment or surfaces that have been in contact with the allergen. (2.4)

For example, cross-contamination can occur when using the same grater to grate cheese and carrots (even with correct hygiene, traces of cheese may remain that are not visible to the naked eye), if you serve this carrot to a person who is allergic to milk. , it may have become contaminated with traces of cheese and, consequently, trigger a reaction. (two)


How to avoid cross contamination?

Cross-contamination should be avoided not only by allergy sufferers and celiacs, but especially by those who prepare and handle food that can be consumed by them.

There are small precautions and simple measures in the preparation and production of food and meals, which can prevent cross-contamination and ensure the ingestion of safe food:

  • If you need to prepare food with and without allergens for the same meal, choose to prepare the allergen-free food first and then the rest.
  • Correct hand and workplace hygiene, equipment, and utensils are essential to minimize the risk of cross-contamination.
  • Wash your hands properly before preparation and between the various stages of food handling, especially if you have come into contact with foods that contain allergens.
  • Do not use the same cooking utensils and containers that you have used to prepare food with allergens. This includes cutlery, mixers, mixers, cutting boards, plates, platters, pots and pans and others.
  • Do not use the same space/bench to prepare food with and without allergens at the same time and properly sanitize the space before preparing food without allergens.
  • Pay attention to the way you thaw or freeze food, so that cross-contamination does not occur. For example, if you thaw in the fridge, leave the allergen food on the bottom shelf to prevent the defrost liquid from dripping onto the safe food and contaminating it.
  • Do not use the same frying oil or cooking water for different foods.
  • During meals, avoid sharing utensils (cutlery, plates, napkins, cups) or direct contact with potentially allergenic foods.
  • If an error has occurred and cross-contamination is suspected, the entire dish should be discarded and a new one prepared. Due to the risk of cross-contamination, removing only the allergen or the portion that came into contact with it from the dish is a high danger. (1.2)


Cross contamination in restoration

Eating out is a major concern for people with allergies and celiac disease, mainly due to the risk of cross-contamination, which is often present in catering establishments, given their particularities and constraints, such as small spaces for preparing and cooking food, sharing constant use of surfaces and utensils, and the simultaneous preparation of several dishes. (3)

There are establishments that pose a greater risk to the allergic patient, such as restaurants with buffet and take-away service, ice cream parlors and bakeries/pastry shops, since the presence of several foods together, as well as the sharing of utensils, favor the possibility of contamination. crusade. (two)

Fried foods and foods with sauces are generally those with the highest risk of cross-contamination. (2.3)


Cross-contamination in supermarkets

In establishments such as grocery stores, super and hypermarkets, cross-contamination can occur in different foods, namely in those that are handled in the store, in the bakery/pastry, butcher, delicatessen, fishmonger, take-away sections, due to the sharing of cutting equipment. and serving utensils or the display of several foods very close together on the same counter.

For safety, you should avoid buying foods in bulk (they may have been cross-contaminated) and all foods that do not contain a list of ingredients. (5)


Cross-contamination in packaged foods

Processed foods often include hidden allergens, which may not be evident from their name or ingredient list. (1)

Cross-contamination in processed foods can happen at all stages of the food chain:

  • In primary production/cultivation of ingredients, for example, when land is shared between plantations of different plant species, as is often the case with soy, wheat, corn or oat plantations side by side on shared land;
  • During transport and/or storage, by sharing the same means of transport and/or storage location for different raw materials or foods;
  • In food production lines, for example when the same equipment is used for the production of milk chocolate and for chocolates with nuts or biscuits (wheat). (1.3)

While many packaged foods currently mention the possibility of cross-contamination on labeling as it is not mandatory, not all companies do so, posing a risk to the most sensitive individuals. Find out more here .


Why is it important to avoid cross-contamination in food?

In order to comply with the food exclusion plan and avoid accidental exposure, it is crucial to identify potentially hidden allergens and identify risky practices, especially with regard to cross-contamination. (two)

In some cases, very small amounts of an allergen may be enough to cause a severe reaction. Ingesting a food that appears to be safe can trigger an allergic reaction with severe consequences, as it has been contaminated with an allergen. (1)


At Fidu we have zero tolerance for the 14 main allergens (where gluten is included). Therefore, we have implemented strict allergen control procedures from the selection of raw materials and suppliers, as well as handling and production in our facilities, in order to eliminate the risk of cross-contamination and guarantee products without traces of allergens, safe for everyone!



  1. Nunes, M., Barros, R., Moreira, P., Moreira, A., Almeida, M. (2012). Food allergy. Ministry of Education and Science - Directorate-General for Education & Ministry of Health - Directorate-General for Health.
  2. Pádua, I., Barros, R., Moreira, P., & Moreira, A. (2016). Food allergy in catering. Lisbon: National Program for the Promotion of Healthy Eating, Directorate-General for Health.
  3. ASAE (2017). Food Allergens. Risks and Foods, vol. 13.
  4. SPAIC Food Allergy Interest Group (2019). Food Allergy: Concepts and Advice and Precautions, 2nd Edition. Lisbon: Portuguese Society of Allergology and Clinical Immunology with support from Thermo Fisher Scientific and BIAL Laboratories.
  5. APN (2014). Diet in Celiac Disease. APN E-Book Collection, vol. 34, Portuguese Association of Nutritionists.