Many publications about sublingual immunotherapy (SLIT) have been cited in recent years. Sublingual immunotherapy is widely used in Europe as a form of desensitization. Desensitization is a method of making a person less sensitive to allergy triggers (for example pollen, dust mites, cat, dog).
Sublingual Immunotherapy is different from Oral Immunotherapy
Some published reports have interchangeably used the term sublingual immunotherapy and oral immunotherapy (OIT). SLIT is a form of desensitization that involves the placement of a specified amount of allergy extract under the tongue and holding it there for a few minutes before swallowing it. In contrast, people that get OIT are instructed to immediately swallow the allergy extract.
The mechanisms of allergic tolerance are different for SLIT compared to OIT. The majority of reports from Europe, where both forms are commonly used, refer to the emerging benefits of SLIT, not OIT. In fact, many allergy experts in Europe do not feel OIT is very effective.
Comparing SLIT and "Allergy Shots"
The following comments address comparisons between SLIT and subcutaneous immunotherapy (SCIT), more commonly known as allergy shots. Allergy shots are the most common means of desensitization used in the United States, most effectively by trained allergy specialists. Recent publications have addressed the effectiveness and safety of SLIT compared to SCIT (under the tongue vs. allergy shot).
The American Academy of Allergy, Asthma and Immunology (of which I am a member) has reviewed and continues to follow many published reports on SLIT.
I recently reviewed published clinical trials on SLIT as well as a few comparison studies on SLIT and SCIT (Journal of Allergy and Immunology 5/2006 p1021). Most of the publications are from Europe. First, allergens in Europe are likely different, to some extent, from allergens in the United States. Second, most of the studies involved small numbers of patients. The small numbers of patients in many of the SLIT trials weaken their results.
In contrast, many studies in the U.S. on patients getting allergy shots involve large numbers of patients.
The results? Less than 40% of the trials on SLIT showed benefit in controlling allergy symptoms and reducing the need for allergy medication. Data on allergy shots studied in the U.S. report more than 50% of the trials to be effective in both areas.
The good news about SLIT is:
1) It does not require a shot (NO NEEDLES!!!)
2) It is a safer means of providing immunotherapy compared to the allergy shots (there's a much lower risk of anaphylaxis)
3) It offers a chance to reduce allergic sensitivity with a home therapy program (fewer office visits).
4) It may allow younger children (under age 5) to be started on immunotherapy, as opposed to allergy shots, where we generally wait until school age before considering them.
5) As seen in many reports on SCIT, some studies have shown long term benefit (reduced allergy or asthma symptoms years after stopping treatment).