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Sublingual Allergen Immunotherapy (SLIT)

Bulent Mamikoglu, M.D.

Last updated: July 9, 2016

In general practice almost two thirds of adults report partial or poor relief with pharmacotherapy for allergic rhinitis. The next step is treating such patients is allergen specific immunotherapy. There are two methods are available: one is traditional subcutaneous allergy injection, the second is the sublingual application of the allergens. This paper will review the sublingual method.

The core difference between sublingual and subcutaneous allergy treatment, is that sublingual treatment is administered through the mouth with drops or tablets, while subcutaneous treatment is with injections. The second major difference is that SLIT is usually done every day, while shots are done every week or other week. Finally, SLIT can be used for self-treatment at home, while allergy shots must generally be administered in a doctors office (Larsen et al, 2015)

How SLIT works:

There remains some controversy about how SLIT works, although it is generally accepted by most allergists, especially in Europe (Allam and Novak, 2014). In sublingual treatment either fixed or increasing dose of allergens is introduced to the immune system. The allergens are picked up by the macrophages located the in the oral mucosa. With activation of the oral macrophages (garbage cells) the balance of immune response is shifted from T2 helper IgE response to T1 cellular response. IgE response causes mast cell discharge of histamine and other chemokines which clinically present with typical allergic reactions of nasal discharge, sneezing, congestion, itching etc.(Wheatly et al: 2015).

Evidence that it works:

Alvarez-Cuesta et al (2007) found that SLIT worked for cat allergy. As subcutaneous desensitation for cat is sometimes painful, this is a useful alternative.

Demoly et al (2015) reported in a double blind, placebo controlled trial that SLIT was effective for dust mite allergy. Soh et al (2016) also found it to be effective.

Technique of SLIT

First one must determine what the patient is allergic to. At Chicago Dizziness and Hearing, allergy tests are performed either by the physician or under direct supervision. Tests includes tree, grass, weed pollens, molds, dust mite and animal danders. We also test common foods.

Sublingual Allergen Specific Immunotherapy (SLIT) is usually combined with pharmacotherapy with antihistamines (example: Allegra, Claritin, Zyrtec) and topical corticosteroids (example Flonase) at the start of the treatment. Usually 3 to 4 months is needed to start to see clinical efficiency and reduction of allergy symptoms. Treatment is continued for 3 to 5 years. After completion of the treatment unlike discontinuation pharmacotherapy, the therapeutic effect continues at least 3 years.

At Chicago Dizziness and Hearing we provide customized allergens based on the patient's allergy testing. The dose is gradually increased with single or multiple antigens until we reach maintenance dose. The benefit of this method is to decrease possible side effects related to the allergen treatment. We mix the allergens into 50 % glycerin solution, taking once daily. We recommend that the patients keep this refrigerated.

Side effects of SLIT are uncommon, other than a tingling sensation of tongue. Headaches, stomach cramps or loose stools are also reported. Anaphylactic reactions (i.e. low blood pressure, shock) with SLIT treatment are very rare.To avoid these symptoms we start in low dose and gradually increase the dose of antigen.

Tablets vs drops

Sublingual allergens are also available as single antigen treatment through pharmaceutical companies as prescriptions. The FDA has approved 3 tablets: Grastek(R), Oralair(R), and Ragwitek. Patients with limited allergies to a single source - -such as for example ragweed -- can benefit from these tablets (Li et al, 2015). For patients with multiple allergies, taking several allergy tablets could be very expensive and may prove difficult to receive approval from insurance. (Pleskovic et al, 2015).

Currently ragweed and grass antigens are available as tablets, and approval for dust mite is pending. In tablet form the sublingual allergy treatment dose is fixed for every patient. Dosing sometimes might be too high for some allergy patients.

Food allergens

SLIT is also available for food allergens. The efficacy of SLIT for food allergy is presently controversial (Pratico et al, 2015). It does not work for peanut (Burks et al, 2015). In Chicago we limit treatment to the most common foods -- milk, egg and wheat allergens.


Reviews have concluded that SLIT is a little safer than subcutaneous immunotherapy (i.e. shots). Insurance coverage is not as good as for shots.



Copyright August 3, 2016 , Timothy C. Hain, M.D. All rights reserved. Last saved on August 3, 2016