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Could Sublingual Immunotherapy Be Used to Treat Food Allergies?
Traditionally, non-food allergies have been treated with a combination of medications and Subcutaneous Immunotherapy (SCIT) or allergy shots. These are weekly or monthly injections containing allergens to which people are allergic. SCIT is the "gold standard" or treatment method against which all other possible therapies are compared.
Sublingual Immunotherapy (SLIT) is a method where a liquid or a tablet is placed under the tongue. This area of the mouth has lots of blood vessels and allows medicines to go directly into the blood stream. SLIT could potentially be safer than shots, could be done at home, and may be easier for children who don't like shots.
Due to the increasing use of SLIT in Europe to treat environmental allergies (EAs) and to the growing interest in SLIT to treat EAs in the U.S., a Joint Task Force of the American College of Allergy, Asthma, and Immunology (ACAAI) along with the American Academy of Allergy, Asthma, and Immunology's (AAAAI) Immunotherapy and Allergy Diagnostic Committee reviewed the available literature on SLIT. This monumental task involved wading through a patchwork quilt of studies to finally find approximately 120 studies that could be compared on the basis of dosing, efficacy, immunologic response, and safety. All of this was compared to the standard of SCIT.
On dosing, they found that doses varied by 30,000 fold, that frequency varied from daily to weekly, and duration of treatment varied from 2 months to 5 years.
With clinical efficacy, they found that although there was evidence of some improvement with SLIT therapy in symptom and/or medication control, over one-third of the studies did not show improvement in either area.
The immunologic response, when the studies did specifically look at them, showed a decrease in circulating eosinophils, decreased serum eosinophilic cationic protein (ECP), reduced development in new skin reactivity, along with improvement in some other markers.
Finally, although there were adverse effects reported, there were no severe systemic reactions resulting in severe drops in blood pressure nor death listed. There was, however, scant study mention of the use of SLIT in patients with severe asthma and multiple allergen SLIT therapy.
The committee concluded in an article published in The Journal of Allergy and Clinical Immunology1 that many questions regarding SLIT use in treating environmental allergies remain unanswered, including effective dose and frequency, how the oral route may actually work on the immune system, length of therapy, safety in high-risk patients, and acceptance of this therapy for payment by health insurance companies. Physicians choosing SLIT to treat patients would have to devise specific instructions for use anticipating all situations that could occur in home-based treatments, to develop methods to ensure patient compliance, and to evaluate how this would affect their practice liability and their patients' ability to pay for likely a very expensive treatment. Further, while there are FDA approved formulations of allergy extracts available, they are permitted for use as an injectable (SCIT) or for diagnostic testing only, not for oral use. Thus if used orally, it would be an unapproved or off-label use.
If comparing SCIT to SLIT for environmental allergens treatment is a bit like comparing apples to oranges, then extending this concept to treating food related allergies would be even more difficult. So many of children with food allergies already have other medical conditions (i.e. reflux, eosinophilic esophagitis, eczema, asthma, oral allergy syndrome) and the possibility of anaphylactic reactions would still be a reality.
There are some efforts toward trials being conducted in the US. Currently there is one study recruiting for candidates in the US (www.clinicaltrials.gov) and two studies outside of the US not yet recruiting for SLIT therapy in dust mite allergies. Also there has been one very small study in Spain2, where a specially prepared hazelnut extract was used in adults and the results were encouraging. There was a decrease in specific IgE levels and a significant increase in the threshold of sensitivity to hazelnut allergen.
In a similar vein, but with a different method of allergen administration are a few small ongoing studies in developing a tolerance to food allergens. The method includes actually ingesting small, precise, increasing doses of the allergen rather than placing it under the tongue as with the SLIT method. These oral methods of administration may be referred to as oral intervention therapy (OIT), specific oral tolerance induction (SOTI), oral desensitization, or oral hyposensitization3.
The peanut study conducted by Dr. Wesley Burks and colleagues at Duke University (North Carolina), gave patients gradually increasing small doses of a peanut protein flour to eat for up to 4 months. The goal was to lessen the sensitivity of the children to peanuts in case of an accidental ingestion. Early results were positive in that some children have tolerated up to 300 mg of peanut protein which is equivalent to about one peanut.
We are hopeful that SLIT may be a treatment option in the future, but it still requires a great deal more study, standardized clinical trials, and data. Please check with your own allergist concerning possible clinical trials, since SLIT therapy is not approved right now by the FDA and is still considered experimental.