In the last twenty years, allergies have spread more and more, so much so that the percentage of allergic children in the country has gone from 7 to 25%, in practice 1 in 4 children may have a form of allergy. Allergy is an organism reaction that occurs when our immune system mistakes a typically harmless substance (allergen) for a aggressive agent to fight.
Pollen, dust mites, milk, eggs and nuts are just some of the most common allergens among young and old that can cause more or less severe symptoms. To be sure that it is an allergy there are special ones allergy test, but they are not all the same and, above all, not all are reliable. Here then is the Prof. ssa Viviana Moschese, Director of the Immunopathology and Pediatric Allergology Unit of the Tor Vergata Polyclinic in the city, comes to our rescue and helps us to clarify the topic of allergy tests for children.
In this article
- allergies and intolerances
- the most common allergens
- how allergies manifest themselves
- allergy test
- skin prick test
- Growth test
- challenge test
- molecular diagnostics
- the tests you don't need
Allergies and intolerances are not the same thing
"The difference between allergies and intolerances is very important, even if there is often a lot of confusion between these two terms" says Prof. Moschese. "When we talk about allergy we mean a reaction that is immune-mediated, that is, it involves an immunological mechanism".
What exactly does it mean? If the child is allergic to something, his body overreacts against a certain substance usually harmless for other people. This substance is called allergenic. Thus, when the body first comes into contact with the allergen, the immune system produces a large amount of immunoglobulin E (IgE), a particular type of antibody. The following times those IgE antibodies specific for that allergen are activated and favor the release of inflammatory substances causing itching, swelling, rhinitis and other typical allergy symptoms.
Allergic manifestations can be mild, with reactions limited to very severe such as anaphylactic shock (especially in the case of food allergies, drug allergies, hymenoptera venom)
In the case of intoleranceson the other hand, the immune system has very little to do with it because it is not involved. The classic example is that of lactose intolerance, now very common, in which the symptoms that the child presents depend on the lack of a particular enzyme necessary to metabolise this substance.Read also: Allergy or coronavirus: how to distinguish them in children
Allergens: which are the most common
The people responsible for allergies can be many and it is not always easy to identify them. "Allergens - explains Moschese - can be mainly of two types:
- inalanti: such as dust mites, molds and pollens from plants and trees (responsible for seasonal allergies, especially in spring);
- food: In the first two years of a child's life, allergies to milk and egg proteins are common. Then over time other allergies such as those towards fish proteins, peanuts and nuts emerge. "
In general, the most common allergens I'm:
- dust mites;
- milk's proteins
- egg proteins;
- fish / shellfish;
- animal hair.
When the child comes into contact with the allergen, the allergic reaction occurs which can manifest itself in various ways.Read also: Allergy to dust mites: the rules for a really clean house
How allergies manifest themselves
Allergic manifestations can be respiratory, gastrointestinal and / or cutaneous depending on how they occur.
"The respiratory allergies can involve rhinitis, conjunctivitis, asthma, while the forms of skin allergy manifest with urticaria, itchy reactions, angioedema, atopic dermatitis. When, on the other hand, the allergic manifestation is of type gastrointestinal, typical symptoms are poor growth in children, as well as vomiting and diarrhea. In some cases it can even lead to anaphylactic shock "says Prof. Moschese.
If the child has one or more symptoms such as asthma that suggest an allergy, it is advisable to speak immediately to the pediatrician who will refer the parents to a pediatric allergist.Read also: Spring allergies and children
How allergies are diagnosed
The specialist, in this case the pediatric allergist, will be able to perform specific allergy tests. "First, however, it is always necessary to carefully evaluate the entire clinical picture, starting with one thorough medical history which also includes family history. In fact, if both parents are allergic there is an increased risk that the child is also allergic. Genetic and environmental factors contribute to the appearance of an allergy that must be considered in the evaluation of the allergic child, "says Moschese.
Once an allergy condition is suspected, diagnostic tests are carried out to assess whether the child has allergic sensitization. But be careful, not all existing tests are really valid.Read also: Nasal washes, are they useful if the child suffers from allergies?
Allergy tests are not all the same
The diagnosis of allergy makes use of some specific tests:
- lo Skin Prick Test;
- the search for specific IgE against the suspected allergen (or Growth test);
- the in vivo oral trigger test (Challenge test for food allergies);
- the search for Molecular specific IgE.
These are the tests to use in those children who may have a respiratory or food allergy. "Also the total IgE dosage it can be useful, but it does not have a highly predictive value, at most it could tell us if there is a predisposition to allergic manifestations ", explains Prof. Moschese.
Lo Skin Prick Test
"The Skin Prick Test represents the first choice test to confirm the clinical suspicion of an IgE allergy mediated by both food and inhalants. "The Skin Prick Test is performed on the baby's skin, more precisely on the inner surface of the forearm.
HOW TO DO IT: "Taxes apply allergen droplets and, through single sterile lancets, the skin is pricked in correspondence with each droplet to evaluate the sensitization to the allergen we want to test "explains Prof. Moschese. After about twenty minutes the reaction can be evaluated: in case of allergy a small bump similar to an insect sting. It is a very simple and relatively inexpensive test.
FEATURES: The Skin Prick Test is safe, it can be performed at any age, but above all it gives reliable results. To assess the correctness of the test, saline solution is applied to one point on the skin (negative control) and a drop of diluted histamine (positive control) is used at another point. More than one can be tested at the same time allergens (both inhalants and food), depending on the clinical history and age of the child.
To perform the Skin Prick Test it is necessary to suspend, at least one week before the exam, theuse of antihistamines.
In some conditions, however, instead of the Skin Prick Test, the allergist may decide to perform the in vitro test with the specific IgE dosage.
The search for specific IgE or Rast test
"This test is a little more invasive for the child because it is done through the blood sample, it is more expensive and you have to wait a little longer for the results, but in some cases we prefer to use this test "says Prof. Moschese.
FEATURES: The search for specific IgE is based on the assumption that a person allergic to a substance present in the blood of the specific antibodies. Specific IgEs are researched and measured against suspected allergens. "This test is a second level exam that is carried out in certain cases:
- when the Prick Test results do not reflect the clinical history (possible false negative);
- in the presence of skin dermographism or extensive dermatitis (possible false positive)
- when antihistamine therapy cannot be stopped;
- when there is a recent history of anaphylaxis ".
The in vivo trigger test or Challenge test
The in vivo challenge test is the test of choice for diagnosing food allergy.
FEATURES: the test is performed by administering to the patient, in increasing doses, the food to which an allergy is suspected and is considered positive when symptoms appear after ingestion (food allergy is demonstrated in vivo). This type of test could cause reactions as serious as it is anaphylactic shock, which is why it must be performed in hospital in the presence of personnel experienced in the management of any reactions.
Innovative molecular diagnostics: the search for specific molecular IgE
This is a more recently introduced test that however, it is not always used in the correct way. "Today - explains Prof. Moschese - we can fortunately also measure the specific molecular IgE, an advance compared to the traditional specific IgE dosage, which allows us to know exactly what is the allergenic protein". As Moschese is keen to point out," this is a great step forward, but it cannot be considered a first choice test to use as a routine examination". The search for specific molecular IgE must always be requested by the specialist for a correct interpretation, especially for food allergies. In short, it is certainly a latest generation test, more expensive, but not necessarily the most suitable and therefore it will be up to the allergist to evaluate case by case whether to use it or not.
The ones listed so far are all tests deemed valid and therefore approved by the scientific community. Unfortunately, however, there are many others on the market that are passed off as "reliable" when in reality they are completely useless if not dangerous.Also read: 12 signs to tell if your child might have allergies
Allergy tests: which ones should not be trusted
"To date, there are far too many tests that have not been validated and that they are useless for the diagnosis of allergies. These tests are generally very expensive, both in economic terms and for the inconvenience they cause to the family. Often following these tests, children are put on a diet by eliminating fundamental nutritional factors, thus causing deleterious effects on the health of the little ones ".
Among those to avoid as reported by the Del Paesena Society of Pediatric Allergy and Immunology:
- the sublingual provocation-neutralization test;
- the cytotoxic test;
- the blood IgG test;
- the kinesiological test;
- the hair test;
- the Vega test;
- various tests on saliva, urine and feces.
If some "specialist" offers you one of these tests to check the presence or absence of an allergy in your child, it is better to forget it and avoid a useless waste of money. All these tests used for the diagnosis of allergies have no proven scientific basis to justify their use. Indeed, as stated above by Prof. Moschese, these tests could lead to the useless exclusion of some essential foods for children or, otherwise, to the failure to recognize a true allergy which could endanger the health of children and young people.
Sources used for the article:
- Advice from Prof. Viviana Moschese, Director of the Pediatric Immunopathology and Allergology Unit of the Tor Vergata Polyclinic in the city;
- Del Paesena Society of Pediatric Allergy and Immunology (SIAIP), "Why alternative allergy tests available in pharmacies are useless";
- Higher Institute of Health, Allergy
- allergies children
- seasonal allergies