What is sublingual immunotherapy (SLIT)?

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Sublingual immunotherapy or SLIT is a common form of immunotherapy that involves application of drops of allergen extracts beneath the tongue. This form of immunotherapy has been utilized in Europe for many years and its usage in other countries recently increased but still not approved in the U.S. SLIT is typically administered as drops or tablets of the allergen extract which are placed under the tongue and then spat out or swallowed.

In studies conducted, swallowing the allergen extract seems to work better. Immunotherapy which is swallowed and not kept under the tongue might cause a number of side effects such as vomiting, diarrhea and nausea, thus it is not used.

Generally, SLIT is administered on a daily basis or several times in a week over a period of years. Most individuals are able to self-administer SLIT at home. Based on studies conducted, the therapy is given before the pollen season, during the pollen season or both or even year-round. Even today, the ideal dosing regimen for SLIT is still not determined.

How SLIT works?

Based on studies conducted, the therapy is given before the pollen season, during the pollen season or both or even year-round.

The immune system of the GI tract tends to tolerate foreign substances. It simply means that it does not respond in an overly active way to swallowed material. This makes sense or else the body would overly react to anything swallowed, including food. Once SLIT is administered into the GI tract, the immune system tolerates the allergen instead of over-reactivity of the immune system. As a result, less allergy symptoms occur once the body is exposed to the allergy source such as animal dander or airborne pollen.

Effectiveness of SLIT

SLIT seems to be efficient in the management of allergic rhinitis, allergic conjunctivitis and even allergic asthma. Even though most studies do not reveal any advantage in the treatment of allergenic disease, the results are rather erratic.

Safety of SLIT

Throughout the years, the safety of SLIT has been documented. There are no severe or fatal reactions to SLIT. On the other hand, minor side effects such as itchy mouth can occur in most individuals while moderate side effects were also documented which includes the following:

  • Irritation of the lip, mouth and tongue
  • Eye itchiness, swelling and redness
  • Sneezing episodes, nasal itchiness and congestion
  • Nausea, vomiting, diarrhea and abdominal cramps
  • Asthma symptoms
  • Urticaria and angioedema

Who are suitable for SLIT?

Individuals who are diagnosed with allergic disease by allergy testing might be considered for SLIT. Take note that young children might be able to tolerate and benefit from SLIT as well as older adults. Pregnant women can continue with the therapy during pregnancy but must not start while pregnant.

Those who have severe asthma should be monitored closely when under SLIT since the asthma symptoms can worsen.

In studies conducted on SLIT, it focused on individuals with one type of allergy such as dust mite or grass. Those who have multiple allergies such as to pollen, mold, animal dander or dust mite might not be suitable candidates for SLIT due to the large volume of various allergen extracts that should be taken.

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