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Allergen: Nuts

Since ancient times, nuts have been consumed by man. They are very energetic foods, rich in proteins, vitamins, fats and trace elements. They are used directly in food in their natural form, roasted, salted or fried, or used as a source of extracting oils for cooking, perfumery, cosmetics or medicine. (1)

Reactions to nuts are very severe and are often responsible for “fatal or near-fatal” anaphylactic reactions. These reactions can happen even after ingestion of small amounts (1,2).

People with a diagnosed nut allergy are usually advised to avoid them for life, but recently it has been shown that 9% of patients who have had reactions have overcome them (2,3). However, people with allergies to various nuts are less likely to outgrow the allergy (3).

The various forms of food allergy to nuts can be classified into:
a) IgE antibody mediated – is the most common, giving rise to an immediate reaction with onset usually within the first 30 minutes and up to 2 hours after exposure to food (ingestion, contact, or inhalation of food particles). It can have a wide range of manifestations. About 90% of immediate allergic reactions to nuts or seeds affect the skin and oral cavity, half involve the respiratory system and 1/3 the gastrointestinal and cardiovascular system (hypotension and loss of consciousness).
b) Not mediated by IgE – involves other immunological mechanisms, namely specific cells or other types of antibodies. It is usually a late reaction, with onset more than 2 hours after food ingestion, and sometimes difficult to diagnose. It can be manifested by gastrointestinal symptoms such as vomiting or diarrhea.
c) Exercise-induced anaphylaxis associated with the ingestion of nuts - in these cases the allergy to a certain nut may only manifest itself after physical exercise. However, a reaction may also occur if the fruit is eaten immediately after exercising.
d) Mixed – involves both IgE and cell-mediated mechanisms, such as in atopic dermatitis and eosinophilic esophagitis. In the case of nuts these forms of allergy seem to be less common. (1)

Cross-reaction of nuts with each other and with other foods:
Among the different nuts, the most frequent sensitizations are to walnuts, hazelnuts, almonds, cashews and pine nuts. It is possible to be allergic to just one or a few nuts and tolerate others (1).
Cross-reaction between nuts is mainly related to botanical family associations, although some studies have reported cross-reactions between nuts without any taxonomic relationship (3). Cross-reaction between allergens occurs when the body mistakenly identifies a similar protein as the protein of the allergen to which it is sensitized, causing the same type of allergic reaction.
Walnut, pecan nut and hazelnut form a strongly reactive group, with walnut and pecan nut being members of the same Juglandaceae family, so they present a stronger cross-reaction (3).
Cashew and pistachio, members of the Anacardiaceae botanical family, also show strong cross-reaction (3). Mango also belongs to the same family and may also cross-react with cashew and pistachio.
Almonds belong to the Rosaceae family, which includes apple, pear, peach, apricot, plum, and cherry (1,3).
25 to 35% of peanut allergy patients are allergic to nuts such as walnuts, cashews or pistachios (1).

When the diagnosis of allergy to nuts is confirmed by the Immunoallergist, the treatment of choice is the total elimination of these foods from the diet. The great difficulty lies in the fact that nuts are often hidden allergens in multiple processed foods. Thus, it is essential to carefully read all food labels (1).

The list of mandatory declaration nuts varies in different parts of the world. In the USA and Canada, the pine nut is classified as a nut, while in Europe it is classified as a seed, not being mandatory to declare as it has not been associated with severe allergies (2,4). In the US, coconut, shea nut and lychee are also on the list of nuts (2). Coconut is a seed that has not normally been restricted in the diets of people with a nut allergy. The medical literature documents a small number of allergic reactions to coconut, with the majority occurring in people who were not allergic to nuts (5).

European legislation requires identification of the presence of nuts on food labels containing almonds (Amygdalus communis L.), hazelnuts (Corylus avellana), walnuts (Juglans regia), cashews (Anacardium occidentale), pecans [Carya illinoiesis (Wangenh.) K. Koch], Brazil nuts (Bertholletia excelsa), pistachios (Pistacia vera), macadamia or Queensland nuts (Macadamia ternifolia) and products based on these fruits, other than nuts used in the preparation of alcoholic distillates, including ethyl alcohol of agricultural origin, which should be understood as an exhaustive list (1,6,7).

Foods That Have or May Contain Nuts: (1, 8, 9)

Fidu_Foods that have or may contain nuts

How to identify nuts on the label:
Nuts, almonds, hazelnuts, walnuts, cashews, pecans, Brazil nuts, pistachios, macadamia or Queensland nuts (7).

Labeling exception:
Nuts used in the preparation of alcoholic distillates, including ethyl alcohol of agricultural origin, are excluded from the mandatory labeling requirement, as studies consider that it is generally recognized that proteins, peptides or fragments will not be transferred to the distillate during a properly controlled distillation. Therefore, spirits made from nuts are unlikely to cause an adverse reaction in individuals who are allergic to nuts (8).

Fidu products do not contain nuts. We do not handle any ingredients in our facilities that may be contaminated with nuts. In this way, we guarantee that there is no cross-contamination by traces and that our products are safe even for the most sensitive.

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Important Note: The content of this article is merely informative and should not replace medical indications. If you suspect that you suffer from this type of allergy, you should seek medical advice.

(1) SPAIC Food Allergy Interest Group, 2017. Food Allergy: Concepts, Advice and Precautions, 1st Edition. Lisbon: Portuguese Society of Allergology and Clinical Immunology with support from Thermo Fisher.
(2) Vieira, R. (2015). Food Allergens: A Synoptic Study. New University of Lisbon.
(3) NDA, 2016. Scientific Opinion on the evaluation of allergenic foods and food ingredients for labeling purposes. EFSA Journal, 12(11).
(4) Allen, KJ, Turner, PJ, Pawankar, R., Taylor, S., Sicherer, S., Lack, G., … Sampson, HA (2014). Precautionary labeling of foods for allergen content: Are we ready for a global framework? World Allergy Organization Journal, 7(10), 1–14.
(5) FARE, 2014. Tips for Avoiding Your Allergen. Food Allergy Research & Education. Available at:
(6) Regulation (EU) No. 1169/2011 of 25 October 2011 of the European Parliament and of the Council of the European Union.
(7) European Commission, 2017. Communication from the Commission of 13 July 2017. Official Journal of the European Union, C428(12 December), 1–5.
(8) 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.
(9) Pádua, I., Barros, R., André, M., & Pedro, M. (2016). Food allergy in catering. National Program for the Promotion of Healthy Eating.
(10) NDA, 2007. Opinion of the Scientific Panel on Dietetic Products, Nutrition and Allergies on a request from the Commission related to a notification from CEPS on distillates made from nuts pursuant to Article 6 paragraph 11 of Directive 2000/13/EC. EFSA Journal, 5(10), 569.