Desensitization involves injecting small quantities of allergen under the skin, with the objective that the body will eventually have almost no reaction when it comes into contact with these allergens.
Allergies are disproportionate immune system reactions that occur when the body comes into contact with a foreign substance (called an allergen) that is normally harmless. In other words, a substance can be harmless to one person but cause an allergic reaction in another.
In the past few decades, health experts have noted a recrudescence in the number of allergy cases. This increase it thought to be due to various environmental factors, namely contact with a greater number of allergenic substances, changes in our dietary habits (consuming foods that are “exotic” and therefore unusual), and the increase in household pets. Genetic factors may also be involved, as a child whose parents have no allergies only has a 15 percent chance of being allergic, while one whose parents both have allergies has a 60 percent chance of also having that problem.
Allergy symptoms vary greatly from one person to the next and depending on the substance at cause. Some individuals only have occasional reactions when they come into contact with the allergen; others who are allergic to substances that are present for whole seasons, however, may have to deal with persistent and bothersome symptoms like a runny nose, watery eyes, difficulty breathing, itching, etc. In order to alleviate these symptoms, doctors may recommend various types of medication, but they are mainly effective when symptoms are mild. There is of course another way to alleviate symptoms: avoiding the allergen. But in many cases, that is easier said than done.
There is, however, a treatment that can help greatly reduce allergic reactions to certain substances like pollen, mites and animal hair. The treatment is called immunotherapy and is also known as desensitization or hyposensitization. The treatment involves injecting small quantities of allergen under the skin, with the objective that the body will eventually have almost no reaction when it comes into contact with these allergens.
Are you a good candidate?
Not all allergies respond to immunotherapy. The ones that respond best are allergies to insect bites and airborne allergens (e.g. pollen, mould, mites). In the case of food, drug or contact allergies, on the other hand, it is advisable to avoid any contact with the allergen, an option that would not be feasible with airborne allergens.
Since desensitization protocols require a lot of motivation on the part of the patient, the latter must have symptoms that are sufficiently bothersome to justify treatment. Indeed, immunotherapy typically lasts three to five years and involves regular visits (usually one or two per week) to the doctor’s office – a rather demanding schedule. Immunotherapy candidates are therefore people whose quality of life is significantly impacted because they cannot control their symptoms with the usual medication (antihistamines, corticosteroids, etc.).
What are you allergic to?
Before your allergies can be treated, you must find out exactly what allergens are involved. To do so, you have to visit an allergist (a physician who specializes in the treatment of allergies). The allergist takes a complete history of your symptoms and the treatments you have used in the past. He or she then administers an allergy test to identify the allergens that are causing your problems. Before diagnosing any allergies or considering immunotherapy, the physician must absolutely establish a clinical association between your history and the results of your allergy tests.
A skin test involves placing a small drop of various allergens on your skin, and then making a pin prick in the middle of each droplet in order to allow the allergen to penetrate the skin. After approximately 20 minutes, the doctor “reads” the results, in other words checks whether there is a local reaction (it usually looks like a mosquito bite). To determine the intensity of the reaction, the allergist compares that reaction to the one you have to a “control” substance (one to which everyone is allergic).
Is immunotherapy complicated?
The allergist uses the skin test results to prepare a “cocktail” of the allergens specific to you. Most patients are allergic to several allergens, but these can usually be grouped into a single vaccine. In order to determine the amount of product to use in the vaccine, as well as the dose to administer, the physician takes into consideration your symptoms, the allergen types and the intensity of your reaction to the skin test.
The treatment itself involves two phases: the initial treatment, followed by a maintenance phase. During the initial treatment, the physician administers increasingly strong vaccine doses until the maximum dose the patient can tolerate is reached. This is the dose that will be used for the maintenance phase. The initial treatment can last several months and usually requires injections once or twice a week.
The maintenance phase involves administering the patient’s maximum tolerable dose on a regular basis (usually once a month or according to the patient’s sensitivity) for as long as four years. The duration varies from one patient to another, but it is rarely less than two years.
If you suffer from seasonal allergies, the treatment usually begins three months before the allergy season begins. Increasingly stronger vaccine doses are injected once a week for nine to twelve weeks. This protocol is repeated before each allergy season for three to five years. If you suffer from aperiodic allergies (i.e. your allergies last all year, as is the case with mite allergies), the treatment will be continuous for three to five years.
Seems like a long time? Don’t forget that allergies last a lifetime. Investing a few years to get rid of them is perhaps not so unreasonable. It is up to each individual to weight the pros and cons of the treatment based on the negative impact that allergies have on quality of life.
The injections are administered subcutaneously on the arm. You should not do any major physical activity for the rest of the day.
It is also essential to stay in the doctor’s office for 30 minutes after the injection – while serious adverse reactions are rare, they can occur at any time – not just early in the treatment. It is therefore imperative that you stay at the physician’s office, where emergency measures are easily accessible.
Without a doubt, the cornerstone of treatment is for the patient to adhere to the treatment. The frequency of the injections must not be altered. The patient must therefore commit right from the beginning to not missing any appointments for the next three to five years.
Does it really work?
Immunotherapy can yield excellent results. It is estimated that 85 to 90 percent of patients respond well to the treatment. It requires a significant investment from the patient, however. It may be several months before it can be determined whether the patient is responding well to the treatment. The physician uses two main criteria to determine how effective the treatment is: a decrease in symptoms and in the need to resort to medication to alleviate these symptoms.
Patients can generally expect to see a notable improvement within the first year of treatment. If that does not occur, the initial allergy diagnosis may have been wrong. The allergist may then perform another skin test to determine whether it is worth continuing the treatment.
Do you get itchy eyes when the trees are budding in the spring? Your pharmacist can suggest an over-the-counter product that should alleviate your symptoms. Are your allergies so severe that you must take medication on a regular basis all year long? You are probably a good candidate for immunotherapy. See your doctor for more information.