So that you understand what food allergies are, I am going to explain how they work. This type of allergy can appear in anyone and at any age, although they are more frequent in the young population. They can also disappear. Those that have been found to disappear most frequently are allergies to milk and eggs that begin in childhood; it is extremely rare for these two allergies to appear in adulthood. And in general, for all foods, the later they appear, the less often they disappear.
In response to your question, I must tell you that it is not whole foods that cause allergies, but some of the proteins they contain. These allergy-causing proteins are called allergens. That is, a person is not allergic to food, eggs, fish, shellfish, nuts, etc. Rather, she is allergic to one or more of the proteins that that food contains.
Proteins are made up of molecules called amino acids. Amino acids form threads, one after the other, and also fold, so they end up with very complex structures. What a person is allergic to is either a certain sequence of amino acids or several amino acids that appear together when they fold. It may happen that in the row that they form in the protein they are not joined together, but when they fold and form a kind of ball they are stuck together, and that group of amino acids that appear together is what the antibodies recognize as an aggressor element for our organism.
Because an allergy occurs like this, when certain antibodies from the immune system detect a specific group of amino acids that they identify as a harmful element for the body and attack it. What we call allergy (to a food or to any other element) is the wrong and disproportionate reaction of our immune system to something that it identifies as an aggressor.
The difference in the size of the reaction that occurs is related to the nature of the specific protein to which one is allergic. In general, proteins that are resistant to heat and enzymes in the digestive tract cause more severe reactions. That is, the specific nature of the specific protein to which one is allergic is what can cause a food to harm an allergic person only on certain occasions. This is explained by two fundamental causes.
If we somehow get a protein to break and those amino acids, which are naturally together, to separate, the immune system will stop detecting it as an aggressor. And that way you can tolerate that certain food. This occurs, for example, with proteins that are denatured by heat. People who are allergic to eggs are often allergic to several proteins. One of them is sensitive to heat, if a person is only allergic to this protein, when the egg is cooked or has undergone some other process with high temperatures, it is tolerated because the protein is denatured.
We have more examples of physical or chemical actions on proteins that cause the protein to break down and that result in people allergic to that specific protein being able to consume the food without having an allergic reaction.
There is another, more complex explanation for why some foods cause allergic reactions only some of the times they are consumed. And it is that there are proteins that need the coexistence of other factors to harm us. There are factors that increase its allergenicity for different reasons, some of which are not well known. The first thing to be described in this regard was exercise-induced allergy to wheat. They are people who eat wheat flour and nothing happens to them, but if they eat some food made with wheat and exercise, it does harm them. This is due to a protein called omega-5 gliadin (ω5G) and people who are allergic to it generally tolerate it under normal conditions, but not when exercising, although we don’t know why.
This, which was first described with this particular protein, has since been seen with others. For example, lipid transfer proteins, present in plant foods, also cause allergies in some people, but only when a cofactor such as exercise appears; Alcohol consumption; take a medication or, in women, the period. In these cases it is very difficult to diagnose because these people observe that they have eaten a food and nothing has happened to them and suddenly it does happen to them and they can take it again, now without the cofactors, and again nothing happens.
These cases are not common, it is normal for the highly selective organism to recognize the protein as soon as it is taken, but they do occur in some people, especially in those who have become sensitized to lipid transfer proteins or are allergic to the ω5G protein.
Ana Fiandor She is head of the allergology section at the La Paz University Hospital in Madrid.
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Coordination and writing:Victoria Bull
we answeris a weekly scientific consultancy, sponsored by theDr. Antoni Esteve Foundationand the programL’Oréal-Unesco ‘For Women in Science’, which answers readers’ questions about science and technology. They are scientists and technologists, members ofAMIT (Association of Women Researchers and Technologists), which answer those questions. Send your questions to[email protected]or by Twitter #werespond.
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