Allergy is an abnormal reaction of the immune system against elements foreign to the body.
To find out more about allergies, see the full information sheet on the subject below.
Allergies: what are they?
Allergy, also called hypersensitivity, is an abnormal reaction of the immune system against elements foreign to the body (allergens), but harmless. It can manifest itself in different regions of the body: on the skin, in the eyes, in the digestive system or in the respiratory tract.
The types of symptoms and their intensity will vary depending on where the allergy occurs, and depending on several other factors specific to each person. They can be very subtle, such as the appearance of redness on the skin, or life-threatening, such as anaphylactic shock.
The main types of allergic manifestations are:
- food allergies;
- asthma, at least in one of its forms, allergic asthma;
- atopic eczema;
- allergic rhinitis;
- certain forms of urticaria;
- anaphylaxis.
People who are allergic are rarely to just one allergen. The allergic reaction can manifest itself in several ways in the same person; allergic rhinitis has been shown to be a risk factor for the development of asthma .
Therefore, a pollen desensitization treatment for hay fever may prevent asthma attacks caused by exposure to these pollens .
The allergic reaction
In most cases, the allergic reaction requires 2 contacts with the allergen.
Awareness
The first time the allergen enters the body, through the skin or through the mucous membranes (eyes, respiratory or digestive tracts), the immune system identifies the foreign element as being dangerous. It starts making specific antibodies against it.
Antibodies or immunoglobulins are substances produced by the immune system. They recognize and destroy certain foreign elements to which the body is exposed. The immune system produces 5 types of immunoglobulins called Ig A, Ig D, Ig E, Ig G and Ig M, which have specific functions. In people with allergies, it is mainly Ig E that are involved.
The allergic reaction
When the allergen enters the body a second time, the immune system is ready to react. Antibodies seek to eliminate the allergen by triggering a set of defense reactions.
The anaphylactic reaction
This allergic reaction, sudden and generalized, affects the whole organism. If not treated quickly, it can progress to anaphylactic shock, i.e. drop in blood pressure, loss of consciousness and possibly death, within minutes.
As soon as the first signs of a serious reaction appear: swelling in the face or mouth, feeling sick, red patches on the body – and as soon as possible before the first signs of respiratory distress appear – difficulty breathing or swallowing, wheezing, change or disappearance of the voice – you must administer epinephrine (EpiPen®, Twinject®) and go to the emergency room as quickly as possible.
atopy
Atopy is a hereditary predisposition to allergies. A person can suffer from several forms of allergies (asthma, rhinitis, eczema, etc.), for unknown reasons.
According to the International Study of Asthma and Allergies in Children, a large study conducted in Europe, 40% to 60% of children with atopic eczema will suffer from respiratory allergies, and 10% to 20 % will have asthma .
The first signs of allergy are often atopic eczema and food allergies, which can appear in infants. Symptoms of allergic rhinitis — sniffles, eye irritation , and nasal congestion — and asthma begin later in infancy .
Allergies: the causes
For there to be an allergy, 2 conditions are essential: the body must be sensitive to a substance, called allergen and this substance must be in the person’s environment.
The most common allergens
Among airborne allergens
Pollen, dust mite droppings and pet dander.
Among the food allergens
Peanuts, cow’s milk, eggs, wheat, soy (soya), tree nuts, sesame, fish, shellfish and sulphites (a preservative).
Other allergens
Medicines, latex, insect venom (bees, wasps, bumblebees, hornets).
Allergic to animal hair?
We are not allergic to hair, but to animal dander or saliva, no more than we are to feathers in pillows and duvets, but rather to the droppings of dust mites that hide there.
We still know little about the origin of allergies. Experts agree that they are caused by a variety of factors. Although there are many cases of family allergies, the majority of children with allergies come from families with no history of allergies .
Therefore, although there is a genetic predisposition, other factors are involved, including: tobacco smoke, Western lifestyle and the environment, including air pollution.
Stress can cause allergy symptoms to appear, but it would not be directly responsible for them.
Milk: allergy or intolerance?
Do not confuse cow’s milk allergy caused by certain milk proteins with lactose intolerance, an inability to digest this milk sugar.
Symptoms of lactose intolerance can be eliminated by consuming lactose-free dairy products or by taking supplements of lactase (Lactaid®), the deficient enzyme, when consuming dairy products.
Allergies: who is affected?
Allergies are much more common today than they were 30 years ago. Worldwide, the prevalence of allergic diseases has doubled over the past 15 to 20 years. From 40% to 50% of the population of industrialized countries is affected by some form of allergy.
In Quebec, according to a report produced by the National Institute of Public Health of Quebec, all types of allergies have experienced a significant increase. The prevalence of allergic rhinitis increased from 6% to 9.4%, asthma from 2.3% to 5% and other allergies from 6.5% to 10.3%.
So what at the beginning of the XX? century, allergic rhinitis affected about 1% of the population of Western Europe, today the proportion of people affected is 15% to 20%.
In some European countries, nearly 1 in 4 children aged 7 or younger has atopic eczema. In addition, more than 10% of children aged 13 and 14 suffer from asthma.
To what can we attribute the progression of allergies?
By observing the social and environmental changes that have marked the last decades, researchers have put forward various hypotheses.
The hygienist hypothesis
According to this hypothesis, the fact of living in an increasingly clean and sanitized environment (homes, places of work and leisure) would explain the increase in the number of cases of allergies in recent decades.
Contact, at a young age, with viruses and bacteria would allow a healthy maturation of the immune system which, otherwise, would tend to allergic reaction. This would explain why children who contract four or five colds a year would be less at risk of allergies.
The permeability of the mucous membranes
According to another hypothesis, allergies are rather the consequence of too great a permeability of the mucous membranes (gastro-intestinal, oral, respiratory) or of a modification of the intestinal flora.
To learn more about the subject, read Allergies: what the experts think.
Allergies: how do they evolve?
Food allergies tend to persist: you often have to ban the food from your diet for the rest of your life. As for respiratory allergies, they can subside to the point of almost completely disappearing, despite the presence of the allergen.
We don’t know why a tolerance can set in, in this case. Atopic eczema also tends to fade over time.
On the contrary, insect venom allergies that occur following stings can worsen, sometimes from the second sting, unless you receive desensitization treatment.
Allergies: how to diagnose them?
The doctor proceeds to a history of the symptoms: at what times, do they appear, and in what way. Skin tests or a blood sample make it possible to precisely discover the allergen in question in order to eliminate it as much as possible from its living environment, and to be able to better treat the allergy.
Skin tests identify the substances that trigger the allergic reaction. They consist of exposing the skin to very small doses of purified allergenic substances; you can test about forty at a time.
These substances can be pollen from various plants, mold, animal dander, dust mites, bee venom, penicillin, etc.
We then observe the signs of an allergic reaction, which can be immediate or delayed (48 hours later, especially for eczema). If there is an allergy, a small red dot appears, similar to an insect bite.
Allergies are manifested by many symptoms.
To learn how to identify them, discover the complete list of symptoms in this sheet.
Allergies: symptoms
Food allergies
Red and white patches on the skin, itching, swelling of the eyes, tongue and face. In more severe allergies, an anaphylactic reaction may occur.
Note: Symptoms usually appear within 30 minutes of eating the food.
asthma
Wheezing, tightness in the chest, difficulty breathing in, and a dry cough. These symptoms occur episodically.
atopic eczema
Red patches with crusts of dry skin and scales, in specific areas of the body, itching.
allergic rhinitis
In the presence of the allergen, itchy and runny nose, itching and redness in the eyes and tension in the sinuses.
hives
A transient rash of pinkish or whitish papules, with itching and burning sensation.
Insect venom allergies
Red rashes, pain and swelling where the bite is, soon after being bitten. In more severe allergies, an anaphylactic reaction may occur.
The anaphylactic reaction
Throat tightness, difficulty breathing, rapid pulse, paleness, nausea, vomiting, or diarrhea. In the event of anaphylactic shock, there is a drop in pressure which can lead to loss of consciousness. Anaphylactic shock can be fatal.
Some people are at higher risk of developing allergies. Also, risk factors favor their appearance.
Discover them here.
Allergies: people at risk
Children with at least one parent, brother or sister suffering from allergies.
Children with eczema and allergic rhinitis at a young age are at higher risk for asthma .
Allergies: risk factors
Smoking
Maternal smoking during pregnancy and exposure to second-hand smoke in early childhood put children at higher risk for asthma .
Pollution
Air pollution is as much a risk factor as an aggravating factor. It causes acute exacerbations of asthma and aggravates allergic rhinitis . Also, climate change would notably have the effect of increasing the production of pollen by plants, in certain regions of the world .
There is no consensus on the following factors. These are interesting hypotheses currently under study.
According to the hygienist hypothesis (see description above), the fact that children acquire fewer viral infections at a very young age would contribute to allergies. Fewer and fewer families – which reduces the exchange of infections between brothers and sisters – live in a more sanitized environment.
Treatments to prevent and treat infections are also more accessible (vaccines, antivirals, antibiotics). A review of studies has shown that children who attend daycare (nursery) contract more infectious diseases, but are less at risk of allergies .
The abandonment of breastfeeding
Breast milk modifies the composition of the infant’s intestinal flora by enriching it with bifidobacteria which would reduce the risk of allergy . Combined with exposure to bacteria and viruses, breastfeeding contributes to the proper maturation of the immune system.
On the other hand, the proteins contained in breast milk would be less irritating for the baby’s intestine and they would make the intestine less sensitive to allergenic molecules.
Too few fruits and vegetables and too many omega-6s
Dietary antioxidants and a good omega-3/omega-6 ratio may be especially important during pregnancy and in infancy .
Experts have noted the following changes in the diets of Westerners:
Reduced consumption of fruits and vegetables. These foods are important sources of antioxidants, for example, vitamin C, vitamin E, carotenoids and selenium. There may be a link between their low consumption and asthma .
A lack of antioxidants in the lungs would make the respiratory system more susceptible to oxidative damage, inflammation and asthma . Thus, a diet low in fruit and vegetables would make individuals more susceptible to allergies.
Increased consumption of omega-6 fatty acids, found mainly in certain vegetable oils (corn oil, sunflower oil and seeds, safflower oil, sesame oil and soybean oil) to the detriment omega-3s (fatty fish, walnuts, flax seeds, etc.) .
The Western diet provides an excess of omega-6, and a deficiency in omega-3: which would cause cardiovascular diseases, allergies and inflammatory diseases . See our Essential fatty acids sheet for more information.
Exposure to moisturizing creams or lotions containing peanut oil during the first 6 months of life may increase the risk of peanut food allergy . Exposure can come from creams applied to the mother’s nipples to relieve chapping caused by breastfeeding, or from creams applied to the skin of infants to treat dry skin, diaper rash, etc.
It seems that creams containing peanut oil are quite numerous on the market. In an American study of 13,971 children, 35% of mothers whose children had a peanut allergy had used this type of cream . To check if a product contains peanut oil, consult its list of ingredients or ask a pharmacist.
Exposure to pet allergens (dander and saliva) does not appear to contribute to the development of allergies in children . On the contrary, according to several cohort studies, children exposed to animals in their first year of life, especially cats and dogs, would be less at risk.
Certain preventive measures can be put in place to prevent the onset of allergies.
Discover them in this sheet.
Allergies: preventive measures
Can we warn?
At the moment, the only recognized preventive measure is to avoid smoking and second-hand smoke. Tobacco smoke would create a breeding ground for various forms of allergies.
Otherwise, we do not know of any other measures that can protect against it: there is no medical consensus in this regard.
Nevertheless, the medical community is exploring various avenues of prevention that could be of interest to parents with allergies who wish to reduce the risk that their child will also suffer from them.
Prevention assumptions
Important. Most of the studies we report on in this section have involved children at high risk for allergies due to family history.
Exclusive breastfeeding
Practiced during the first 3 to 4 months of life, or even the first 6 months, it would reduce the risk of allergies during early childhood. However, according to the authors of a review of studies, it is not certain that the preventive effect is maintained in the long term.
The beneficial effect of breast milk may be due to its action on the infant’s intestinal wall. Indeed, growth factors present in milk, as well as maternal immune components, would contribute to the maturation of the intestinal mucosa.
Thus, it would be less likely to let allergens into the body. It should be noted that there are non-allergenic milk formulas on the market, to be preferred by mothers of children at risk of allergies who do not breastfeed.
Delay the introduction of solid foods
The recommended age for introducing solid foods (eg cereal) to babies is around 6 months. It is considered that before this age, the immune system is still immature, which increases the risk of suffering from allergies.
However, the scientific evidence is insufficient to be able to confirm this beyond any doubt.
Interesting fact: children who eat fish from their first year of life are less prone to allergies.
Delay the introduction of highly allergenic foods
Allergenic foods (peanuts, eggs, shellfish, etc.) could also be given with caution or avoided while making sure not to cause dietary deficiencies in the child. It is important for this to follow the advice of a doctor or dietitian.
The Quebec Association of Food Allergies (AQAA) publishes a calendar that can be referred to for the introduction of solid foods, which begins at 6 months.
However, be aware that this practice is not based on solid evidence.
Hypoallergenic diet during pregnancy
Intended for mothers, this diet requires avoiding major allergenic foods, such as cow’s milk, eggs and nuts, in order to avoid exposure to the fetus and infant.
A meta-analysis by the Cochrane Group concluded that the hypoallergenic diet during pregnancy (in women at high risk) is not effective in reducing the risk of atopic eczema, and may even lead to malnutrition problems in the mother and the fetus. This conclusion is supported by other summaries of studies.
However, it would be an effective and safer measure when adopted only during breastfeeding. Following a hypoallergenic diet while breastfeeding requires supervision by a healthcare professional.
In a study with a control group, researchers tested the effect of a hypoallergenic diet followed during the third trimester of pregnancy and continued until the introduction of solid foods, at the age of 6 months, among 165 mother-child couples at risk of allergies.
The children also followed a hypoallergenic diet (no cow’s milk before one year, no eggs before two years and no nuts and fish before three years). At 2 years, children in the “hypoallergenic diet” group were less likely to suffer from food allergies and atopic eczema than those in the control group. However, at 7 years, no difference in terms of allergies was noted between the 2 groups.
Measures to prevent recurrences
- Regularly wash bedding in case of allergy to dust mites;
- ventilate the rooms frequently by opening the windows, except perhaps in the case of seasonal allergies to pollen;
- maintain low humidity in rooms conducive to the development of mold (bathroom);
- do not adopt pets known to cause allergies: cats, birds, etc. Give up animals already present for adoption.
Depending on the type of allergy, the doctor will suggest various medications that will alleviate the symptoms.
Discover all the possible treatments to treat allergies here.
Allergies: treatments
Some general remarks
The first step in allergy treatment is to identify the allergen (for example, pollen, animals, mold, dust mites, or certain foods) and avoid it if possible.
Depending on the type of allergy, the doctor will suggest various medications that will alleviate the symptoms and improve the quality of life.
Allergy medications come in the form of pills, liquids, nasal sprays, eye drops, and topical creams. Some are available over the counter, others by prescription.
In case of food allergy, the only possible treatment is to stop consuming the food for the rest of your life. People with a strong food allergy, usually to nuts, peanuts, fish or shellfish, which can cause anaphylactic shock, should keep an epinephrine auto-injector (EpiPen®, Twinject®) handy.
Epinephrine slows down the allergic reaction, the time to get medical attention. Note that allergies to latex, certain medications and insect bites can also cause anaphylactic shock.
Main types of drugs
Antihistamines relieve symptoms by blocking the release of histamine. Most are available over the counter, such as Claritin®, Zyrtec®, Réactine® and Allegra®.
Decongestants, such as Sudafed® and Balminil®, relieve nasal and sinus congestion.
Antileukotrienes, drugs obtained by prescription, block the effects of leukotrienes (Singulair®, Accolate®). Leukotrienes, belonging to prostaglandins, are produced by the immune system during an allergic reaction, and contribute to the onset of symptoms.
The use of corticosteroids is reserved for more serious allergy problems. They prevent and treat inflammation. They can only be obtained by prescription (Flonase®, Nasonex®, Dermacort®, Prednisone®).
Side effect: Some of these medications may cause drowsiness. Ask your pharmacist.
Nasal shower is a practice that contributes to the relief of nasal and sinus congestion. It consists of successively rinsing each nostril with a commercial (for example, Salinex®) or homemade saline solution. To make your own saline solution, dissolve a quarter of a teaspoon of salt in 500 ml of warm water. The liquid is then introduced into the nostril using a pear that can be obtained in pharmacies.
Desensitization treatment
Desensitization treatment is mainly used in cases of severe insect venom allergy and allergic rhinitis, when medications are insufficient to relieve it or when adverse drug reactions are poorly tolerated.
It consists of administering repeated and increasing doses of the allergen, over a period of three to five years. The desensitization treatment makes it possible to accustom the organism to the presence of the allergen and thus to reduce the intensity of the allergic reaction.
According to experts from the Mayo Clinic in the United States, this therapy has demonstrated good efficacy in cases of allergy to cats, house dust mites and pollen. In children, desensitization therapy may reduce the risk of asthma.
However, it should not be attempted if you have a food allergy, as it can cause a severe anaphylactic reaction.
Medical treatments for food allergies
No treatment possible. Avoidance of allergenic foods, injection of epinephrine in case of severe allergic reaction. See the Food Allergies fact sheet for more details.
Medical treatments for asthma
Antileukotrienes, bronchodilators (fast-acting or slow-acting beta-agonists , theophylline, ipratropium bromide, etc.), corticosteroids.
See the Asthma fact sheet for more details.
Medical treatments for eczema
Corticosteroids (topical or oral), antihistamines, cyclosporine, tacrolimus, pimecrolimus, antibiotics, ultraviolet treatment, psychotherapeutic approaches, skin care.
See the Eczema sheet for more details.
Medical treatments for allergic rhinitis
Antihistamines, decongestants, nasal or oral corticosteroids, antidegranulants, antileukotrienes, desensitization treatment, surgery.
See the Allergic Rhinitis sheet for more details.
As part of its quality approach, Passeportsanté.net invites you to discover the opinion of a health professional.
Dr. Jacques Allard, general practitioner, gives you his opinion on allergies.
Allergies: the opinion of Dr Jacques Allard
“Allergic reactions are extremely common. The intensity of symptoms varies between people and the severity of the allergy.
If you suffer from allergic rhinitis and the symptoms are bothersome, I advise you to first consult a doctor to find the allergen in question. Most often, this is done through skin testing.
Thereafter, it will obviously be necessary to avoid this allergen as far as possible. If necessary, medication can relieve symptoms.
But if the symptoms persist and the drugs are ineffective or cause too many side effects, desensitization treatment can be used.
If you suffer from insect venom allergy, you must consult a doctor and always have an epinephrine auto-injector on hand. It could save your life. In addition, desensitization is often indicated.
Finally, if you suffer from a food allergy, you have no choice but to avoid consuming the food for the rest of your life.
If you have ever had a serious allergy, such as an anaphylactic reaction (swelling in the face or mouth, difficulty breathing or swallowing, wheezing, etc.), you should also always have an epinephrine auto-injector handy. from the hand.”
Dr. Jacques Allard, MD, FCMFC
In the event of allergies, certain complementary approaches make it possible to treat them in a more natural way.
Check out the list here.
Allergies: complementary approaches
Consult the Food allergies, Asthma, Eczema and Allergic rhinitis sheets to find out the details of the complementary approaches specific to each of them. Several natural health products and certain therapies can help prevent or relieve their symptoms.
Certain measures could help prevent allergies in general, in children at risk (one or both parents of whom suffer from allergies).
Researchers believe that it is important to intervene before their immune system becomes mature and exposure to allergens (food, pollen, poison ivy, etc.) causes allergies.
We now know that allergens can cross the placenta and reach the fetus.
Probiotics
Probiotics promote healthy maturation of the child’s immune system, to the detriment of allergic reactions. Some believe they may help prevent other allergy problems, but there is no evidence to support this .
A literature review has reviewed the clinical data on the impact of probiotics, prebiotics and synbiotics (combination of pro- and prebiotics) on the prevention of allergies. The authors point out that it is difficult to draw a definitive conclusion on their effects, due to the heterogeneity of the protocols used.
Nevertheless, when probiotics are taken by the pregnant woman, then by the newborn, they would prevent the onset of allergies in the child. This effect would only be significant during the first 2 years of the child’s life.
More specific studies indicate that probiotics may help prevent atopic eczema in children at risk. In studies, treatment was sometimes given to the mother during pregnancy and continued in the child after birth.
The effectiveness of probiotics may vary depending on the type of probiotics used. Given the variety of probiotics and dosages used in clinical studies, it is impossible at this time to suggest a dosage.
Anthroposophy
The “anthroposophical” lifestyle could help prevent allergies, according to 2 small studies.
By comparing 2 groups of children aged 5 to 13, researchers found a lower prevalence of allergies in children who lived according to anthroposophical principles: fewer antibiotics, fewer vaccinations and higher vegetable consumption ” lactofermented”.
Moreover, Anthroposophic families seem less affected by allergies and other atopic diseases than families that do not follow these principles.
Fish oils during pregnancy
The decline in the consumption of omega-3 fatty acids is one of the major changes in the diets of Westerners in recent decades.
Once the allergy has set in, the effect of omega-3s on symptoms would be very limited, hence the importance of intervening early, believe the researchers.
Only a few studies have looked at the effect of taking fish oil supplements during pregnancy on the risk of allergies in children. According to a synthesis of studies, the results obtained so far are promising 5 .
