Food allergies and intolerance fall into the category of adverse reactions to foods, which includes, in turn, all diseases and disorders caused by the ingestion of certain foods, additives or food contaminants. These adverse responses can be classified into two large groups, toxic reactions and non-toxic reactions. This last group (non-toxic) is not caused by the presence of particular adverse substances but, despite that is harmless for most people, it can cause serious problems for some individuals. Food allergies are a classic example of non-adverse reactions toxic.
The body of allergy sufferers is sensitized towards some food substances, commonly referred to as allergens or antigens. To say that a person is sensitised against an alimentary antigen is equivalent to stating that your body produces antibodies to some normally harmless substances, contained in one or more food.
Adverse reactions on different type of allergic are then mediated by the immune system. Some people develop an allergy to peanuts, kiwi and chi chi to milk, but most people can consume these foods without having problems.
Food allergies can be divided into non IgE mediated and IgE mediated. These are the most common, since many allergic reactions involve immunoglobulins E ( IgE or regains).
The second category of adverse reactions to foods, including toxic type of reactions or “poisoning”, is related to the presence, in a given food or food products, of one or more toxins, such as those of the puffer fish, potatoes sprouting , in amanita phalloides, and some inadequately sterilized canned (botulism). In this case the toxicity is common to all individuals, if that ingested a dose of toxin sufficient to trigger the symptoms.
Toxic reactions to foods are always related to the dose, they not involve the immune system and reaction is proportional to the ingested amount .
In other situations, like lactose intolerance, a food is toxic only for some individuals. Who is lactose intolerant, for example, can withstand fairly low doses of milk, if taken extraordinarily high doses could be toxic to the vast majority of individuals. In same case water can be toxic and even deadly if taken in large quantities (over 10-12 liters per day). In this case, since the intolerance resulting from consumption of foods free of toxins, fall into the category of the adverse reactions of non-toxic type.
Differences between allergies and food intolerance
Allergy is a very complex phenomenon, which begins with a first step, called “awareness”. This condition develops when the body comes into contact with one or more proteins from food which are not recognised by body, and body mark them as dangerous. As a result, body begins to produce specific antibodies IgE class, to try to neutralize them. These antibodies then interact with specific receptors on the surface of mast cells. The awareness-raising phase is clinically silent but, from this point on, whenever the body comes into contact with the Antigen to which is sensitized, trigger the allergic reaction. This event is characterized by degranulation of mast cells, which triggers a cascade of events associated with the release of chemical mediators, including the well-known histamine.
An allergic reaction can lash out immediately, and within a few seconds of exposure to the Antigen, or appear only after a certain period of time (the cat hair allergy may occur even at 24 hours apart). In principle, food allergies appear fairly quickly.
As previously mentioned, a peculiar feature of food allergies is that once sensitized by the body, just a minimal dose of Antigen can trigger allergic reaction, which in certain cases can be hard and dangerous to health. The allergic individual must therefore be especially careful to limit as much as possible contacts with the food to which it is sensitized.
Since a “simple” food intolerance can cause some typical symptoms of food allergies-like nausea, vomiting, diarrhea and abdominal cramps-many people tend to confuse the two terms. In fact, food intolerance, unlike allergies, are always related to a dose, which everyone should know to avoid dug hole. Another key difference is that in food intolerance is never involved the immune system, although in many cases the symptoms, in some respects similar to that of allergies, suggests the opposite.
In most cases, food intolerance is related to dysfunctions of enzyme type. Therefore, the enzyme deficiency or lack of enzymes needed to digest certain substances. Particularly well-known is the lactase deficiency, a protein necessary for the digestion of milk and sugar whose shortage leads to rampant lactose intolerance.
Pseudoallergic reactions have all the characteristics of allergies, but do not involve the immune system. They are caused by food rich in tyramine or histamine, or they are able to stimulate the release of histamine by the organism. The release of these chemical mediators represents the end point of the cascade of allergic reactions and it is responsible for reaction like typical skin manifestations, respiratory, gastro-intestinal tract etc.
Strawberry intolerance belongs to the category of pseudoallergic reactions, because this food, similarly to tomatoes and shellfish, stimulates the release of histamine. Once ingested, these foods, through allergenic disempowered, can mimic an allergic reaction from the point of view of symptoms. Such gatherings are controlled through antihistamine therapy and have specific hazards to the health of the individual (which are typical for a food allergy ). By consuming these foods can appear skin rush (red dots on the skin, itching) but, once we stop consuming, symptoms subside quickly. The amount capable of triggering the allergic reaction vary from person to person depending on the individual predisposition.
Despite many people have adverse reactions to certain foods, allergic diseases are less common than you might think. Nevertheless, the number of people who suffer from food allergies is in continued increase. A major problem is that currently affects approximately 2-7% of adults and 6-13% of children.
Far superior is the incidence of food intolerance (e.g. lactose, reaches, in some ethnic groups, values greater than 90%), but as we have repeated on many occasions, it should not be confused with allergies because it does not involve the immune system.
Allergies risk factors
Inheritance or genetic predisposition to develop allergic reactions to ingestion or inhalation of allergens, is more frequent in families with allergies. This does not mean that food allergies are transferred from generation to generation according to Mendel’s genetic laws. But that statistic data in shows that the children of allergic parents are more likely to develop them. It has been calculated that the risk of atopy for a child with both parents allergic varies between 47 and 100%, against a 13 percent of children without previous allergy history in family.
This inheritance has however some peculiar characteristics:
-symptoms can change considerably from parents to children, both in severity and location of the symptoms (e.g. parent, when it suffers an allergic reaction, respiratory disorders can complain, while the son can suffer skin rush);
-the allergy can develop towards completely different antigens. The parent, for example, may be allergic to the drugs, while the son can share this common towards pollen or food.
Whenever the body comes into contact with an Antigen, and then with a protein that is not properer, produces antibodies against it. Theoretically, then, our bodies should react and develop antibodies in all food proteins, since food represents our most intimate contact with the external environment. This, fortunately, occurs with pathogens but not with food, because the immune system recognizes food proteins as foreign substances but harmless, with a defined tolerance mechanism, involving the intestinal mucosa and the associated lymphoid tissue (GALT, also referred as Gut Associated Lymphoid Tissue). Thanks to this mechanism, most people can take any food without negative allergic reactions.
When we eat, the food arrives in the stomach and begins to be digested, especially its protein fraction. The digestion of food proteins is completed in the intestine, with the release of oligopeptides and individual amino acids that will then be absorbed to mucosal layer and used with plastic function. It can however happen that some incompletely digested protein fragments, with a medium-high molecular weight, are absorbed by the intestinal mucosa. If these fragments contain a epitop sequence, i.e. a series of amino acids linked together to form a protein chain known as alien, may cause sensitisation and, when the food is eaten again, cause the appearance of those symptomatic events typically associated with food allergy. This normally does not occur because of the level of intestinal mucosa secretory immunoglobulin A (IgAs), which neutralize these protein fragments from reaching systemic level and carry out its allergenic potential. This mechanism is called tolerance.
In the presence of the damaged intestinal mucosa (gastrointestinal diseases of inflammatory origin, infection, malabsorption, etc.), insufficient digestive enzymes proteolytic action or debilitating immune system protein fragments to high molecular weight can escape this outpost and reach the systemic level, stimulating the synthesis of immunoglobulins of type e. In this case, there was an initial awareness, that allergic reactions followed real coinciding of future food intake.
Allergies and age factors
|Allergies and age factors
Something that is considered pathological in adulthood (poor functionality of enzyme systems and reduced immune response) is extremely common in the neonatal period. When is born, the baby’s immune system is still incomplete. An early weaning can then determine the onset of food allergies, primarily because the enzyme function is not yet complete (some are not perfectly digested proteins) and secondly because the intestinal mucosa is not yet fully efficient (can be knocked by food antigens); same goes for the immune system.
It is therefore no coincidence that most allergies are manifested in the first period of life .Fortunately, within 3 years, there was a regression in 44-87% of cases, resulting in desensitization of the organism. Conversely, as later appears the allergy is the lower the probability of a spontaneous regression.
Allergies and environmental factors
There are many environmental factors that may interfere with the severity of symptoms associated with allergic reactions. Some of these, for example, become more severe in winter, because cold stimulates the production of histamine which, when added to the histamine level released during the allergic reactions, causes more noticeable symptoms.In the presence of multiple antigens, the allergic manifestation becomes more intense when multiple allergens are present simultaneously.The incidence of food allergies is growing, especially in industrialized countries. The blame is often given to various environmental factors, like smog, stress, exercise and smoking. We have seen, in fact, that these factors have no role in the development of allergic diseases and, although they may increase the synthesis of endogenous histamine and make the most obvious manifestations, this factors cannot be considered as main factors for incidence of diseases of allergic nature.
The main factors involved in this worrisome phenomenon should be instead sought in excessive hygiene and reduced family size. Statistics show that in small families children are more likely to develop allergies than those who live in bigger families. Another interesting aspect is that the percentage of allergies in developed countries is proportional to GDP: the more country is richer the more is the percentage of allergic people . The same report also applies within the single household, where the incidence of allergic reaction is directly proportional to the socio-economic level. The explanation should be precisely excessive enlistment hygiene level compared to the past, as a reduced exposure to antigens.
The use of vaccines, disinfectants and antibiotics preserves us from many diseases, on the other hand, when used in manic mode, it don’t stimulate the immune system.The immune system is not in contact with its „natural enemies“. So get bored too diverts his attention to food allergens. Pharmacological studies have shown that under normal conditions, T lymphocytes produce gamma interferon, which in turn stimulates the production of antibacterial and antiviral antibodies or natural killer cells. In an environment dominated by excessive hygiene instead increased production of immunoglobulins and antibodies, i.e. those are directly responsible for food allergies.
Geographical areas and eating habits
There are more frequent allergies that exist in certain geographical areas and others that are more common in different areas; everything seems related to the eating habits of the local population. This is because if there is the greater consumption of a certain food it is much greater chance that we can raise „awareness“ to it. Allergy to rice, for example, is virtually unknown in Italy and in Europe, but it is very frequent in Asian countries, where the diet is almost exclusively based on the consumption of this cereal. Similar is food allergy to peanuts, one of the most frequent in the United States where there is high consumption of this food. In particular, its incidence is so high as to make it a real social problem (you’re considering the possibility of including in public facilities, such as airports, areas where it is forbidden the consumption of peanut, since simply inhaling food particles can promote the emergence of allergy). The same is becoming very common in Europe, especially in northern countries.
Animals and plants that are phylogenetically close or belonging to the same family (goat and sheep’s milk or tomato and eggplant), can have very similar DNA regions. If these regions are coded for protein fractions epitopiche, in which is also the antibody recognition, the cross reactivity is virtually certain. This phenomenon explains why someone who is allergic to tomatoes is so often allergic to eggplant Who is allergic to a certain food must therefore pay close attention to similar foods from phylogenetic point of view.
In food processing it is a widespread use of soy lecithin that, because its emulsifying agents, represents a typical ingredient of many food products.. Who is allergic to soy must therefore be particularly attentive even to those products to which is added as an additive in the form of derivatives (lecithin, but also protein hydrolysates).
This danger has placed an increased focus on the labelling of food products. The so-called directive imposes allergens, for example, to warn consumers of the possible presence of allergens, specifying it on the label. Thanks to this directive it is not uncommon to find on the packaging labels such as “produced in an establishment where is produced dried fruit”. If the system has not been adequately sanitized before conversion can indeed happen that small residual particles contaminate the product, turning it into a potential health risk to people allergic to, for example, peanuts.
|Allergies And Transgenic Foods
In preparing a transgenic plant are often placed fragments of DNA from another botanical species. If this DNA fragment encoding a sequence epitopica it may happen that the transgenic plant has an allergenic power, normally absent in its natural counterpart.
An example is soy that has transgenic origin. There are in fact registered cases of people that are not allergic have suffered an allergic reaction to soy. It is then seen that this reaction was actually due to an allergy to Brazilian walnut, whose DNA had been used for soybean transgenic production.
With the increasing spread of GMO foods, for allergic person then becomes hard to understand what can and what cannot eat.
Symptoms of food allergies
The symptoms of food allergies are variable for its localization and intensity; typically involves the respiratory, gastrointestinal and skin. The mast cells, that as a result of interaction with IgE release histamine (the molecule responsible for many effects associated with allergic manifestation), are particularly abundant at organs such as nose, throat, lungs, skin and gastro-intestinal tract.
The consequence that is more frightening than a food allergy is anaphylactic shock, which in more severe forms can lead to respiratory obstruction, coma and death of the individual and requires, therefore, early intervention with epinephrine or adrenaline.
Signs and symptoms of food allergy, which fortunately are annoying but not always so dangerous, occur on average from a few minutes up to an hour after the end of the meal.
In children, allergic reactions more frequently (70%) involve the gastrointestinal tract, but can also occur skin disorders (24%) and respiratory (6%). The result is the most fearsome anaphylactic shock, which can often be triggered by small amounts of food.
The diagnosis of food allergies
Diagnosis is based on clinical trials of various kinds, and on careful analysis of the patients medical history. In general, we prefer to start with skin tests, evaluating the appearance of allergic reactions after inserting under skin antigens of different sorts. Once it is found food allergen in test, you can make specific in vitro test, to find out which protein fragments are responsible for allergy.
Many diagnostic techniques are available today, with different degree of complexity and evolving in order to obtain innovative methods with greater accuracy and reliability. In many cases, in fact, allergen research is hampered by several factors, including that of the co-sensitization. There is Increasingly number of people with allergies that have negative common diagnostic tests; This phenomenon occurs especially when the individual is sensitive to different substances, but in mild measure, and reveals that allergic reactions only when exposed simultaneously to multiple allergens.
It can also happen that a person allergic to a raw food but not to cooked, since many allergens, with protein nature, are inactivated by heat. Another factor that may complicate the diagnostic and identification of the allergen is represented by the use of complex foods, i.e. consisting of many ingredients and food additives.Once diagnosed allergy, food or foods should be eliminated from the diet.
Care and treatment
As anticipated, the treatment of food allergy is based on the elimination of the food from diet to which the subject is sensitized. This particular diet, defined exclusion diet, doesn’t have to last a lifetime because, especially in young children, the symptoms tend to disappear over time.
In the presence of an allergy, your doctor may prescribe injectable epinephrine, that person must bring all the time to face the eventual appearance of an anaphylactic shock.
Food allergies with low degree of severity can be controlled through the use of antihistamines, after exposure to allergen to mitigate unwanted events.
List of the most allergenic foods
FAO (Food and Agriculture Organization), in collaboration with the European Commission, made a list of the most allergenic foods.
The 90% of allergic reactions of food base are caused by eight foods, let’s see them in detail.
- milk: an allergy to cow’s milk proteins is the leading cause of food allergy and mainly affects children. Can give rise to very serious also reactions even through simple particle inhalation of powdered milk
- Soy: is another strongly allergenic food; some children allergic to cow’s milk are also allergic to soy, as the “milk” that is obtained by pressing its seeds is often used as a hypoallergenic alternative to milk.Don’t forget, also, that some components, such as soy lecithin and protein hydrolysates, are widely used as food additives and can then make dangerous food consumption to which are added.
- eggs: egg contains many proteins with potential allergic effect. Among these, the main onesare: three, ovalbumin, ovomucoid and the diferric; only the last two are heat labile and denaturing with cooking, losing the ability to produce allergic reactions.
The same allergens present in the egg are also contained in the meat and especially in that of chicken, which can be consumed safely as long as it is cooked.
The egg allergy is common allergy in childhood but, fortunately, regresses with ease.
- fish: fish is one of the most common food allergies in developing countries in Scandinavia. If after a meal of fish body reacts it is important to perform a series of diagnostic tests to find out if it is a pesudoallergic reaction or a real allergy (many fish are source of histamine)
- peanuts and nuts: Peanut Allergy until a few years ago was a problem restricted to the United States, now is spreading in Europe and is becoming one of the leading baby’s allergies.
- Mollusks: are very rare. Of particular interest are the reactions to some species of land snails, improperly called “snails”, occurring in susceptible to dermatofagoidi.
- Wheat: wheat flour only exceptionally causes allergic reactions. Wheat allergy should not be confused with Celiac disease, which, while involving the immune system, being a disease autoimmune-based represents an entirely different disease.
- fruit: foods like banana, avocado, chestnut, melon, kiwi, strawberries, can provoke allergic reactions. But also vegetables like celery, which represents one of the most common foods responsible for allergies.
In this case who is allergic to a product must perform precise clinical trials for the fruits of the same botanical family.
Some fruits and vegetables are able to unleash a mild allergic reaction, characterised by a nagging sense of itching on the palate and throat, which appears in contact with the food. This is a typical example of cross-reactivity (or cross-reactivity), the phenomenon in which different foods can cause similar allergic reactions because they contain antigens with protein sequences. In particular, the allergens present in some fruits and vegetables are similar to those contained in some pollens. For example, people allergic to ragweed, can also be to melons, as well as the persons allergic to birch pollen can have allergic reactions to apples.
Substances and additives in foods can also implicate allergic or intolerance reactions:
- Salicylates: naturally present in some foods like dried fruits, berries, oranges, grapes, aromatic herbs, wine and spirits. Can cause forms of chronic urticaria.
- Tetrazine is a synthetic dye, reported on the label under his own name or code E102, added to foods to give them a pleasant lemon yellow. Present in a variety of preparations including several drinks, mayonnaise and puddings, can cause urticaria and asthma
- Sulphur dioxide: used to treat grapes and musts, is an additive which can be found in many foods such as jams, juices, vinegar, fruit salads and salads treated in restaurants with spray to maintain a cooler appearance;
Sulfites, metasolfiti and bisolfiti: added to prepackaged products as preservatives and/or antioxidants as dangerous, especially for asthmatics.