Nuts are, with fruits, the first cause of food allergy in adults and one of the first causes in children.
What are Nuts?
Nuts belong to different and unrelated botanical families. Most are fruits (almond, hazelnut, walnut, pistachio, chestnut and macadamia nut), some are seeds (sunflower seeds, pumpkin seeds and pine nut) and in recent years, Brazil nut and cashew, both considered fruits, have been included in our diet.
Nuts have a high nutritional power and are very important in the diet. They are consumed directly in dried form or as part of bakery and pastry products, in ice cream, in sauces or oils.
What are the nuts that produce the most allergy?
Unlike what is popularly thought, the repeated consumption of a food increases the risk of developing allergy to that food, it is for this reason that the nuts that produce the most allergy are the most consumed. In our midst, hazelnut, walnut and almond are the nuts that most often cause allergic reactions.
Why are they a major cause of food allergy?
Nuts are important in the field of allergy for several reasons, including:
a) they are one of the main causes of allergic reactions to food,
b) They frequently produce severe reactions, which can be life-threatening
c) It is one of the most frequent causes of anaphylaxis
d) They are hidden allergens and small amounts can produce serious reactions and
e) They are a frequent cause of cross-reactivity with other nuts or with other plant foods.
Who is responsible for nut allergy?
Foods are made up of a diversity of nutrients, such as carbohydrates, vitamins and proteins. It is the latter, proteins, that have the ability to develop reactions in allergic people. In the case of nuts there are 2 main groups of proteins, storage proteins and lipid transfer proteins (LTP). LTP’s are the proteins that are most often related to severe reactions in the Mediterranean area.
What about peanuts?
Peanuts, although consumed as a nut, belongs to the legume family. Legumes are plants characterized by the fact that their fruits are enclosed in pods.
Peanut allergy is a real public health problem in Anglo-Saxon countries due to its high consumption. It is estimated that in these countries 50% of peanut allergy reactions are severe, associating respiratory distress, arterial hypotension, and in some cases death. In our environment the consumption of peanuts is increasing day by day, so in the coming years it is expected that cases of peanut allergy will also increase.
Unlike other foods, in which the increase in temperature during cooking degrades the proteins responsible for allergic reactions, in the case of peanuts it has been proven that heat increases the ability to develop allergic reactions, that is, once roasted, the peanut becomes more “allergenic” and increases its resistance to gastric digestion processes.
What symptoms does nut allergy produce?
Symptoms can vary from individual to individual, as well as their severity and intensity. Some allergy patientes may have itching in the oral cavity, tongue, and lips (oral allergy syndrome). In addition to itching, the presence of lip edema, lip and cheek erythema is common. The itching can spread to the ear canals and throat. In general, these symptoms appear when the oral mucosa comes into contact with the nut.
Sometimes oral symptoms may be followed by skin manifestations with the presence of redness, itching and hives (urticaria). Digestive tract involvement can present as abdominal pain, vomiting and diarrhea. The airway could also be compromised producing cough, tightness of the chest, choking and wheezing. Finally, when the reaction is severe, it can alter blood pressure, producing a rapid drop in blood pressure (anaphylactic shock) that is usually accompanied by generalized paleness and cold sweating. Some allergy patients may also have rhinoconjunctival symptoms, such as sneezing, mucus, nasal congestion, itchy eyes, and watery eyes.
Symptoms can develop minutes after ingesting the nut, or take a few hours. The symptoms that appear immediately, before 15 minutes of ingestion of the food, are usually of mild intensity and disappear within a few minutes of its onset (oral allergy syndrome). The progress of oral symptoms with involvement of the skin, digestive and respiratory system are signs of poor prognosis, since in the case of serious reactions that affect more than one system (anaphylaxis) their resolution requires emergency medical attention. In general, most reactions due to allergy to nuts occur in the first 60 minutes after ingestion of the food, although there are cases in which the reactions have occurred 3-4 hours later.
Who can have more severe reactions?
Patients with multiple food allergies are considered to have a higher risk of more severe reactions than those with only a certain food allergy. In the Anglo-Saxon population, peanut allergy is considered a risk factor for developing serious or fatal reactions, being one of the most frequent causes of anaphylaxis.
Severe reactions to nuts are more frequent in asthmatics, with previous episodes of severe reactions and in those who have had reactions with minimal amounts of nuts (traces).
As with other food allergies, the severity of nut allergy reactions can be influenced by cofactors such as sleep deprivation, physical exercise, menstruation, or the concomitant use of alcohol or non-steroidal anti-inflammatory drugs ( NSAIDs). All of these cofactors increase the risk of serious reactions.
Are there differences between children and adults?
Allergy to a single nut is more common in children of younger age, while adult patients have allergy to multiple nuts. It is believed that these differences are due to the fact that, during growth and development, from childhood to adult life, there is a progressive exposure to these foods, this repeated exposure being responsible for the development of new allergies.
How is nut allergy diagnosed?
The medical history plays a fundamental role in the diagnosis of food allergy. A detailed clinical history can exclude multiple causes of allergic reactions, thus allowing all efforts to be concentrated on those most suspicious agents.
Skin tests (prick test) with suspicious foods is the first step in the allergy study, but it must be remembered that a positive result only indicates “sensitization” and not necessarily allergy. This is followed by the detection of specific antibodies in the blood. Currently, it is possible to detect specific antibodies for the main proteins responsible for allergic reactions (molecular diagnosis).
In some cases it is necessary to do skin tests with fresh food (prick by prick). This technique is used in situations when skin tests and antibody detection are not available for the suspect food or when there are divergences between the tests results.
Finally, an oral challenge test may be performed to confirm or rule out allergy to the suspected nut. This test carries risks, so it is performed only in some cases, in a controlled environment, in a hospital facility and always under the supervision of an allergy specialist..
Is there any treatment?
As with other types of food allergy, the only treatment currently available is strict avoidance of the food involved. Therefore, the first recommendation involves eliminating implicated nut rom the diet.
Allergic reactions to nuts are treated like any allergic reaction. The use of adrenaline can save lives in cases of severe reactions. If the patient has suffered a severe reaction to nuts or there is a risk of accidental ingestion, it is advisable to have self-injectable adrenaline devices.
In recent years, “vaccines” have been tested to treat peanut and hazelnut allergy. These “vaccines” have managed to significantly increase the amount of nuts that allergy patients can tolerate, thus reducing the risk of severe allergic reactions caused by ingestion. At the moment it is a line of treatment that is under investigation and that is not yet commercialized.
Programs are also being developed using monoclonal anti-IgE antibodies. These antibodies can modify the immune system and create tolerance to foods that were previously allergic to. At the moment this treatment is limited to children and adolescents with severe food reactions, which are life-threatening.
Can nut allergy be prevented?
At the moment there is no measure to prevent the development of food allergies, but there are measures to avoid the accidental consumption of certain potentially allergenic foods. For some years now, all foods containing peanuts and nuts that are marketed in the European area must specify this on the label. This rule applies both to packaged foods, as well as to those presented unpackaged, as well as to foods prepared for immediate consumption (restaurant menu).
What about nut-free diets?
In the past, it was proposed, as a measure to avoid future allergy in children, the elimination by the mother of foods considered to be more allergenic (milk, egg, nuts) during the third trimester of gestation and during breastfeeding, as well as the delay in the introduction of high-risk foods into the child’s diet. The current international consensus does not recommend these measures, since it has not shown any effect on the prevention of allergic diseases, while it can lead to a nutritional deficit for mother and child.
One last recommendation?
Patients allergic to peanuts must take special care in reading the labels of manufactured products, since it is one of the legumes (along with soy) that are most commonly found as part of additives from other foods (hidden allergens).
We must take into account the widespread use of nuts in sauces, ice cream, pastries or oils, which can be sources of hidden allergens causing accidental reactions.
Minimal amounts (traces) can be tolerated by most people allergic to nuts, but there is a small group of allergy patientes who may have allergic reactions with these amounts; so the recommendations about the consumption or avoidance of traces must be individualized for each case.
Dr Federico de la Roca Pinzón
Allergy Specialist
ClinicAL