Allergies
Definition
Allergy is caused by a person's reaction to environmental molecules or particles called "allergens."
They are present all around us, but do not affect everyone in the same way. They are found in dust mites, pollen, insects, foods, medications, etc. The immune system causes inflammation leading to various symptoms, such as:
Asthma
Rhinitis
Urticaria
Eczema
Swellings
Etc.
They can affect different parts of the body such as the nose, eyes, lungs, skin, etc. Although the allergy is often not serious, there are certain fatal forms which must then be treated urgently.
The main allergies
Allergic Rhinitis and Conjunctivitis
Allergic rhinitis is a chronic rhinitis, defined by the WHO (World Health Organization) as an inflammation of the nasal mucosa induced by allergens, which can be subdivided, according to the mode of occurrence, into: intermittent, persistent and occupational rhinitis.
Rhinitis is clinically characterized by at least two of the following symptoms: nasal obstruction, rhinorrhea, sneezing, nasal pruritus and/or posterior nasal discharge. Rhinitis is frequently associated with ocular (conjunctivitis) or bronchial (asthma) symptoms.
The etiological diagnosis of intermittent pollen rhinitis is often easy, based essentially on clinical history, nasal examination and immediate allergy skin tests. The dosage of source-specific and/or molecular unit IgE is useful in cases of polysensitization.
The etiological diagnosis of persistent rhinitis is more complex and requires looking not only for allergenic sensitizations, but also for associated irritant factors. These factors are important to know because they are also aggravating factors, which should be identified and managed for each patient. These include viral infections, pollution, and associated sinus disorders.
A complete allergy assessment is therefore necessary to establish the etiological diagnosis and facilitate therapeutic management. It is based on a precise interview and some additional examinations.
Apart from allergic rhinitis we distinguish:
Pregnancy and/or hormonal rhinitis
Eosinophilic rhinitis
Rhinitis medicamentosa
Occupational rhinitis
The management of rhinitis is gradual, taking into account the severity and the etiological mechanism:
Mild intermittent or persistent rhinitis:
- H1 antihistamines, oral or local;
- Washing the nose with salt water.
Intramuscular injections and local infiltrations of corticosteroids are not indicated (potentially severe general and local side effects).
Moderate to severe intermittent rhinitis:
- H1 antihistamines, oral or local;
- Nasal corticosteroids;
- Allergen immunotherapy.
Targeted anamnesis
Targeted anamnesis and dietary survey targeting food and medication intake over 4 hours before the allergic reaction are essential. The prick test and/or specific or molecular IgE diagnostic assessment can help in diagnostic orientation.
Oral challenge tests
Oral food challenge tests (OPT) are the gold standard for diagnosing food allergies. These tests must follow a rigorous procedure and must be carried out in appropriate facilities specializing in the management of allergic reactions. They are potentially dangerous and require close monitoring of the patient.
Early oral exposure
Early oral exposure to food allergens such as egg or peanut, during a specific period (between 4 and 11 months), in order to prevent allergies has recently been the subject of interventional studies which suggest that this strategy is beneficial.
Food allergy treatment
The treatment of food allergy is based on the avoidance of the food(s) identified by the well-conducted allergy assessment. In the absence of spontaneous healing, recent management discusses therapeutic approaches to induce tolerance of the food in question.
Food allergies and intolerances
As distinct from allergies, food intolerances are clinical reactions caused by the inability to digest and absorb certain food ingredients.
Intestinal disorders
The intestinal disorders that they can cause in some patients do not of course come from an immunological mechanism. Food IgGs are not involved. The symptoms are purely digestive and non-specific, occurring more than an hour after a meal, such as bloating, abdominal pain, belching, meteorism, flatulence, diarrhea. They are recurrent, at least once a week. Any atypical symptom (weight loss, rectal bleeding, anorexia, anemia, onset after 50 years, associated autoimmunity, etc.) should lead to a search for an organic digestive disease by a gastroenterologist.
FODMAPs
The concept of FODMAP does not reside in food allergies but rather in intolerances. This type of pathology is managed by gastroenterologists. For FODMAP intolerance as in the case of LACTOSE intolerance, allergy tests are not necessary.
Food allergology
Food allergy is often used incorrectly to refer to a series of reactions, secondary to the ingestion of food, whether or not they are of an immunological nature.
True food allergy refers to various clinical aspects secondary to hypersensitivity reactions, most often dependent on IgE, to a food allergen.
Other hypersensitivity mechanisms (types III and IV) may also be involved.
Food allergy is now defined as a loss (or lack of acquisition) of immunological tolerance to a food allergen.
The pathophysiological mechanisms of food allergy arise from an aberrant immune response to ingested food antigens that come into contact with gut-associated lymphoid tissue (GALT). This excessive, allergic-type response overrides the active physiological phenomenon of oral tolerance of food antigens.
The clinical pictures of AA are different depending on age:
In adults
The manifestations are more severe, with a frequency of anaphylaxis of the order of 25%; they also include the classic oral allergy syndrome, during pollen/food cross-allergies.
In children
The main symptoms are atopic dermatitis and acute urticaria. Anaphylactic shock is rarer, although it is increasing in children, in the order of 8 to 10%.
Wasp or bee sting allergy
Sensitization to hymenoptera venoms is common. Several studies report the presence of specific serum IgE and positive skin tests in 10 to 40% of the general population, without all of these subjects necessarily having a systemic allergic reaction to a sting (Sturm, 2008).
The frequency of occurrence of extensive local reactions varies from 2 to 26% in the general population.
The frequency of systemic reactions occurring after a hymenoptera sting has been evaluated in numerous surveys; they report a frequency of 0.3 to 7.5% in the general population (Bilo, 2009), in children and 35-50% of patients who have already had a systemic reaction before and not treated with allergen immunotherapy.
In beekeepers, general reactions could reach 15 to 43% of these highly exposed subjects (Müller, 1990).
Systemic reactions occur in 22-49% of adults and 6-9% of children with mast cell activation syndrome. They represent 1-7.9% of patients allergic to hymenoptera venoms (Bonadona, 2016).
Stages I (or mild) and II (or moderate)
Represents moderate general reactions without associated cardio-respiratory manifestations: urticaria, edema with or without subjective feelings of malaise, chest tightness, anxiety, etc.
Immediate systemic reactions are classified into 4 stages of severity according to the Ring and Messmer or Müller classifications:
Stages III and IV (or severe)
They are the most severe, they are life-threatening and require immediate treatment with adrenaline.
At stage IV
The cardiovascular collapse of anaphylactic shock is in the foreground, urticaria often only appears during the repair phase; it indicates the allergic origin of the accident.
Possibly an antihistamine;
Possibly a fast-acting inhaled β2 mimetic.
For severe reactions with a proven allergic mechanism, the treatment of choice is desensitization (subcutaneous allergen immunotherapy).
Desensitization usually results in healing, including the absence of a severe reaction during a subsequent sting.
The desensitization protocol is based on the repetitive injection of an increasing amount of venom leading to the induction of tolerance.
The diagnosis is based on the precise anamnesis and on the performance of specific IgE biological tests as well as the dosage of mast cell tryptase.
The main purpose of mast cell tryptase assay is to identify patients with Mast Cell Activation Syndrome - a major risk factor in severe systemic reactions.
In case of an initial local, extensive or systemic reaction
the prescription of an emergency kit will be systematic; it includes:
Possibly an oral or injectable glucocorticoid, the use of which is not urgent and only in cases of upper airway involvement;
Self-injectable adrenaline, mainly JEXT® or EpiPen®, the use of which must be meticulously explained and written in a separate document;
Anaphylaxis
Anaphylaxis is a rapid, generalized, often unpredictable allergic reaction that can lead to death within minutes if an injection of epinephrine (JEXT or EPIPEN) is not given.
Symptoms of anaphylaxis can affect multiple organs, including the skin, respiratory, gastrointestinal, and cardiovascular systems upon contact with an allergen.
The situation is URGENT and requires immediate use of the epinephrine auto-injector.
Diagnosis in allergology
Respiratory function tests
(EFR)
These are tests that measure the lungs' ability to breathe in and out of air, as well as how efficiently they transfer oxygen into the blood.
The prick test
It is a skin test that detects allergies by introducing a small amount of allergenic extract into the skin.
Reading takes 15-30 minutes.
The native food prick test
It is a skin test that detects food allergies using fresh foods that are applied to the skin.
Reading takes 15-30 minutes.
L'IgE Microarray
(ISAC)
It is a blood test that detects allergies by using microarray technology to measure the amount of specific IgE to multiple allergens at the same time (approximately 120 allergens analyzed concomitantly).
Specific IgE
It is a blood test that detects allergies by measuring the amount of allergen-specific immunoglobulin E (IgE) in the blood.
The Oral Provocation Test
This is a test that detects food or drug allergies by observing the immune system's response to a specific drug. The oral challenge test involves giving a food to which the person is suspected of being allergic by mouth. Small amounts of the food are started and gradually increased during the test.
Your treatment proposals
Antihistamines
These are medications used to treat allergies by blocking the action of histamine, a chemical released by the body in response to an allergy.
Nasal corticosteroids
These are medications used to treat allergies by reducing inflammation in the nasal passages. They can help relieve symptoms such as sneezing, itching, and stuffy nose.
Aerosol therapy
It is the administration of medications by inhalation. This method allows the medications to act directly on the airways, which can be useful in the treatment of asthma and other respiratory diseases.
Anti-leukotrienes
These are drugs used to treat asthma by blocking the action of leukotrienes, chemicals released by the body that can cause inflammation in the airways.
Monoclonal antibodies
These are medications used to treat allergies by specifically targeting the cells responsible for the allergic reaction. They can help reduce symptoms and prevent future allergic reactions.