Sublingual immunotherapy
Sublingual immunotherapy (SLIT) is a treatment approach for allergies that involves placing allergen solutions, such as pollen extracts, under the tongue. This method is primarily used for allergic rhinitis but also shows potential for treating allergic asthma, latex allergies, and certain food allergies. SLIT operates similarly to traditional allergy shots, where small amounts of allergens are introduced to help "train" the immune system to respond differently, thereby reducing allergic reactions.
One of the notable advantages of SLIT over allergy shots is the absence of needles, making it less invasive and more convenient for home administration. Research has shown that SLIT can effectively alleviate symptoms of hay fever, with studies indicating significant improvements in nasal congestion and itchy eyes among participants. Additionally, prolonged treatment may enhance efficacy, suggesting that annual or year-round use might yield the best results.
While generally considered safer than conventional allergy shots, SLIT can cause mild side effects such as oral itching or gastrointestinal discomfort. Severe allergic reactions are rare, although caution is advised for individuals with high-risk asthma. The method has gained FDA approval for specific allergens, yet further research is encouraged to expand its applications.
Sublingual immunotherapy
DEFINITION: Treatment of allergies by placing an allergen solution, such as pollen extract, under the tongue.
PRINCIPAL PROPOSED USE: Allergic rhinitis
OTHER PROPOSED USES: Allergic asthma, latex allergy, food allergies, other forms of allergy
Overview
Sublingual immunotherapy (SLIT) is a method of treating allergies that closely resembles conventional “allergy shots.” In both methods, small amounts of allergenic substances are administered periodically and over time through a route different from that in which the body ordinarily encounters them. For example, plant pollens ordinarily cause allergic reactions when inhaled. With allergy shots, pollen extracts are injected under the skin, while in SLIT, they are placed under the tongue.
The immune system has many components, but only one of them, the IgE/eosinophil system, produces typical allergic reactions. The alternate routes of administration are intended to “train” other branches of the immune system to neutralize allergens before the IgE/eosinophil system can react to their presence.
The great potential advantage of SLIT over allergy shots is that SLIT does not involve needles which makes it less unpleasant and capable of being done at home rather than at a doctor’s office. The absence of needles may also explain why SLIT has long been categorized as a form of alternative rather than conventional medicine.
There are no universally accepted criteria by which a treatment is classified as part of alternative rather than conventional medicine. Some treatments, such as acupuncture, fall in the alternative category because they belong to a system of medicine considerably unlike that of the modern conventional system; others, like traditional herbology, fall in the alternative category because they involve unprocessed “natural” substances rather than drugs; still others are considered alternative simply because they have been rejected for one reason or another by conventional medicine or have been adopted by practitioners of other forms of alternative medicine.
Scientific Evidence
Perhaps the best evidence for the effectiveness of SLIT involves treatment of allergic rhinitis (hay fever). In a double-blind study of 855 adults with grass allergies, SLIT, using grass pollen tablets for approximately eighteen weeks, markedly reduced allergy symptoms, including nasal congestion and itchy eyes. Marked benefits for most common hay fever symptoms were also seen in another double-blind study enrolling 634 people. In a third double-blind study involving 105 persons, SLIT led to a significant improvement over placebo in symptoms of rhinitis and conjunctivitis from grass and rye pollen allergies. Skin reactivity to these allergens, a more objective sign of allergy, also showed a more substantial reduction in persons using SLIT. Other studies have also shown benefits for hay fever caused by grass pollen or other allergens, including dust mites and tree pollen.
As with conventional allergy shots for hay fever, it appears that if SLIT is, in fact, effective, it must be used for a long time for best results. Three years of treatment may be better than two, and two years better than one. To provide benefits for grass allergy season, SLIT must begin a minimum of eight weeks before the onset of the grass allergy season; even longer lead times produce even better results. Putting all this evidence together, it appears that SLIT may work best if used every year and year-round.
One study suggests that SLIT is not only effective for treating allergies, but it also may help prevent the development of new allergies or mild persistent asthma in children with allergic rhinitis or intermittent asthma. SLIT has also shown promise for latex allergy, food allergies, and other forms of allergy.
Safety Issues
SLIT appears to be safer than conventional allergy shots. The most frequently reported adverse effects include oral itching or swelling and gastrointestinal upset; in the majority of cases, these side effects are mild and short-lived. In one study, 12 percent of people with allergic rhinitis or asthma experienced worsening symptoms at some point in their treatment. Severe allergic reactions appear to occur rarely. However, SLIT has not been fully tested in people with high-risk asthma. The US FDA approved a SLIT tablet for ragweed pollen, timothy grass pollen, northern grass pollen, and dust mites, but further research is needed for other uses.
Bibliography
Baba, Shahid M., et al. "Effectiveness of Sublingual Immunotherapy in the Treatment of HDM-Induced Nasobronchial Allergies: A 3-Year Randomized Case-Control Study From Kashmir." Frontiers in Immunology, vol. 12, Oct. 2021, p. 723814, doi:10.3389/fimmu.2021.723814.
Boltansky, Howard. "Sublingual Immunotherapy - Allergy Drops." Johns Hopkins Medicine, www.hopkinsmedicine.org/health/conditions-and-diseases/seasonal-allergies/could-allergy-drops-be-the-key-to-allergy-relief. Accessed 21 Sept. 2024.
Dahl, R., et al. "Sublingual Grass Allergen Tablet Immunotherapy Provides Sustained Clinical Benefit with Progressive Immunologic Changes over Two Years." Journal of Allergy and Clinical Immunology, vol. 121, 2008, pp. 512-518.
"Immunotherapy with Allergy Tablets." American College of Allergy, Asthma, and Immunology, 28 Feb. 2017, acaai.org/allergies/management-treatment/allergy-immunotherapy/slit. Accessed 21 Sept. 2024.
Marogna, M., et al. "Preventive Effects of Sublingual Immunotherapy in Childhood." Annals of Allergy, Asthma, and Immunology, vol. 101, 2008, pp. 206-211.
Saporta, Diego. "Sublingual Immunotherapy: A Useful Tool for the Allergist in Private Practice." BioMed Research International, 2016, p. 9323804, doi:10.1155/2016/9323804.
"SLIT Treatment for Allergic Rhinitis Nothing to Sneeze About." American Academy of Allergy, Asthma & Immunology, 2024, www.aaaai.org/tools-for-the-public/conditions-library/allergies/slit-treatment-for-allergic-rhinitis-nothing-to-sn. Accessed 21 Sept. 2024.
UNC Health. "Novel Peanut Allergy Treatment Shown to Be Safe, Effective and Lasting." The University of North Carolina at Chapel Hill, 28 Mar. 2023, www.unc.edu/posts/2023/03/28/novel-peanut-allergy-treatment-shown-to-be-safe-effective-and-lasting. Accessed 21 Sept. 2024.