How does allergy desensitization work?

In 70 to 80% of cases, desensitization can significantly reduce the symptoms of allergy. This is performed by subcutaneous injection under medical supervision or by sublingual intake, depending on the results of the allergological assessment. What allergies? The pollen? Acarians ? Food allergies (peanuts, fruit, etc.)? Hair from cats, dogs? How does it work concretely?

What is the definition of allergy desensitization?

Desensitization is a method of treatment of allergies which consists of reaccustoming the body to tolerate the allergen in question. “This is done after an initial phase ofadministration of increasing doses of purified allergens, until the maximum effective dose is obtained which will allow this induction of tolerance to obtain in the long term a reduction or even a disappearance of sensitization to the allergenexplains Dr. Eric Thomas, skin allergist. The allergic person will then present significantly reduced or even disappeared symptoms in the presence of the allergen(s) to which he is sensitive.“.

What allergies can you be desensitized for?

Not all allergies are eligible for desensitization. This treatment can only be offered in the case of:

• Of the pollen allergies (trees, grasses, herbaceous)
• Allergies to mites (domestic, agricultural)
• Allergies to mold
• Allergies to certain animals (cat, dog) and with Hymenoptera venom (wasps, bee).

Several allergens can be used during desensitization. Certain debilitating food allergens (milk, peanuts, nuts) can also be treated, but the results are inconsistent.

To desensitize from an allergy to pollens?

Desensitization (or specific immunotherapy) may be indicated for pollen allergies. It consists in administering, for several years, extracts of allergens (in this case extracts of the pollen(s) to which you react) in progressive doses, so as to stimulate the immune system and to make the person tolerant to the substance. This makes it possible to permanently restore a normal reaction of the body when it comes into contact with allergenic pollen and therefore the absence of symptoms. Desensitization is possible in adults and in children from 5 years old and can be offered to patients:

• If we have identified (with skin tests and a blood test) the pollen or pollens in question.
• If the symptoms remain bothersome despite taking symptomatic treatments.
• If you are in this situation, you can make an appointment with the allergist to determine the usefulness of this type of treatment for you or for your child.

To desensitize yourself from an allergy to dust mites?

Specific immunotherapy (desensitization) would have been proven for many years indicates an article from the Swiss Medical Journal. Specific subcutaneous immunotherapy (SCIT) by dust mite extracts is the only treatment that can cure dust mite allergic rhinitis or asthma. It allows monosensitized children to limit the development of new sensitizations to other aeroallergens. Eventually, it can prevent worsening of symptoms like the onset of asthma in a patient with only rhinitis. Sublingual immunotherapy (SLIT) could also be effective, even if the results of the studies are contradictory (the effectiveness of the desensitization depends on the level of allergens administered).

Desensitization spreads over a period of 3 to 5 years. There are two different modes of administration:

► The sublingual route (desensitization under the tongue): this method, now used in more than 8 out of 10 casesconsists in depositing a few drops or tablets under the tongue then let them melt for two minutes without swallowing. The treatment is taken periodically at home according to a protocol prescribed by the allergist, depending on the patient’s tolerance to the treatment.

► Injections (desensitization in the form of injections): the best known and oldest method, desensitization in the form of injections consists of injectingallergenic extract in the upper arm with syringes and fine needles. The injection is done monthly on average. “It must be carried out by a doctor or a nurse under medical supervision, says Dr. Thomas. Currently in France this form of administration is limited to Hymenoptera venoms (wasps, bees)“.

Who to consult for a desensitization?

The allergist is the essential interlocutor for the choice and the follow-up.

How effective is desensitization?

In 70 to 80% of cases, desensitization makes it possible to significantly reduce allergy symptoms. “Numerous studies have demonstrated the preventive effect on the onset of asthma as well as the prevention of secondary sensitization to other allergens.“, adds our expert.

How long do the effects of desensitization last?

If it varies from person to person, there is an effect beneficial in the long term of the treatment. It happens that seasonal booster cures indicated over a few years, if the symptoms return persistently over prolonged periods.

What are the dangers and side effects of desensitization?

A bucco-pharyngeal intolerance (oral, lingual, pharyngeal itching) or even labial swelling may be observed, before which a dose adjustment can be proposed. Episodes of cough, relapse of rhinitis or even asthma or urticaria are exceptional. “To date, no documented severe reactions have been observed. Many studies have shown general tolerance of allergen vaccines in a majority of patients“, specifies the allergist.

For whom desensitization is contraindicated?

Desensitization is in principle not offered:

• in case of autoimmune diseases or cancers (according to a precautionary principle),
• in children under 5 years of age (correct intake is not guaranteed).
• it will be interrupted in the event of poor tolerance after several attempts by the patient (often correlated with ineffectiveness), in case of ineffectiveness after 1 year of treatment, and also in case of regular non-compliance (which cannot guarantee effectiveness). In these 3 situations the injectable route could be an alternative.

Thanks to Dr. Eric Thomas, skin allergist at the DermoMedicalCenter.