What is sublingual immunotherapy (SLIT)?

SLIT is a treatment option for allergic rhinitis (also known as hay fever), which is characterized by sneezing, itchy watery nose/eyes, nasal congestion and rhinorrhea in relation to an allergen in the environment (i.e., pollens, animals etc.).  While many people get relief from standard therapies such as oral antihistamines or nasal corticosteroids, those who do not may benefit from subcutaneous immunotherapy (SCIT or allergy shots) or SLIT.  As opposed to SCIT, SLIT involves administering the allergen in a liquid or tablet formulation under the tongue daily.  The efficacy of SLIT is similar to SCIT. However, it is only effective in controlling symptoms related to the allergen being administered, unlike antihistamines or corticosteroids, which are nonspecific medications that dampen the immune reaction.

Is SLIT available for all environmental allergens?

No, at present the only FDA-approved SLIT tablets are for grass pollen (GRASTEK and ORALAIR), ragweed pollen (RAGWITEK) and dust mite (ODACTRA).  Currently, SLIT is only approved to be used a single formulation at a time. In other words, people who are allergic to multiple allergens should generally only receive SLIT for one of those allergens at a time or consider SCIT.  In SCIT, allergists do have the flexibility to include multiple allergens in administered shots. While there are products available that mix multiple allergens into a sublingual drop, these are not FDA approved as they have not been rigorously evaluated for efficacy and safety, and therefore, are not currently recommended by national academic allergy societies.

When should I consider referring a patient for SLIT?

Patients who have uncontrolled allergic rhinitis despite standard therapy (nasal corticosteroids are typically first line therapy) can be referred for aeroallergen testing by an allergist to confirm diagnosis and consideration of additional therapies such as SLIT.  As detailed above, SLIT is only approved for single allergens, so ideal candidates for SLIT are patients with allergic rhinitis that is primarily driven by a single environmental allergen. 

What are the side effects of SLIT?

SLIT is generally safe and well tolerated. After a first test dose monitored in the office, it can be given at home, in contrast to SCIT which should always be administered in a medical facility because of the need to quickly recognize and treat anaphylactic reactions. The most common side effects include localized itching or tingling of the mouth and lips or mild gastrointestinal symptoms. Systemic reactions to SLIT, although much rarer than with SCIT, can happen. Patients should be prescribed an epinephrine autoinjector and be trained in their use.

SLIT is also contraindicated in certain medical conditions including severe and/or uncontrolled asthma, a history of a severe systemic reaction to any form of immunotherapy, a history of a severe local reaction to SLIT, eosinophilic esophagitis, or any condition which might impair a patient’s ability to survive a severe reaction.  Therefore, while it is typically well tolerated, SLIT should be prescribed under the guidance of an allergist.

How long do patients need to take SLIT?

For SLIT products targeting seasonal allergens, it is typically recommended to start 12-16 weeks before the relevant pollen season and continue throughout the season.  SLIT products to perennial aeroallergens (i.e., dust mite) may be taken year-round.  The duration that an individual patient is on SLIT varies and is up to the discretion of their allergist, but evidence suggests that three years of SLIT can help induce clinical benefit and immunological changes that can be maintained for two-three years after stopping therapy.


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