Sublingual Immunotherapy (SLIT)

Introduction

The use of SLIT to treat allergies in the U.S. was first documented in the early 1900s. Use has steadily grown in recent decades. Today, thousands of allergists, ENT allergists and physicians provide SLIT therapies to U.S. patients. In Europe, SLIT has grown to be a dominant treatment method. Please note, as SLIT is not currently FDA approved, billing for SLIT is entirely out-of-pocket. Allergy testing will still be covered by insurance.

How SLIT Works

The area under the tongue is considered a privileged domain due to its dual properties: It is rich in T-cells and other antigen presenting cells that help induce tolerance, while poor in mast and other effector cells which can trigger reactions. The area also exhibits the highest permeability of any easily accessible mucosal surface – making it prime for delivering fast-acting medication and effective vaccines. Given the large number of dendritic cells in the mucosal area where foreign proteins are first introduced, the area plays a pivotal role in developing tolerance versus sensitization.

Basic Info on SLIT

  • Due to its excellent safety profile, ease of administration, and economic considerations, SLIT is becoming a favored form of allergen-specific immunotherapy.

  • Long-lasting tolerance is achieved after two to four years of SLIT, typically in patients with persistent perennial nasal allergies and also those with asthma. 

  • Immunotherapy for periods less than three years may be associated with symptom relapse after one year of treatment cessation 

  • Significant clinical improvement has been observed at four months and at 10-12 months of SLIT

  • Frequent and regular administration of sublingual immunotherapy may prove conducive to immune cell conditioning and may be the reason SLIT is devoid of the side effects associated with SCIT

  • SLIT has been found to be useful for infants and children, including those with eczema and recurrent ear infections; severe asthmatics; patients with chronic sinusitis; patients with food and mold allergies; anaphylactic patients; patients with multiple severe allergies; and those who are averse to needles or would otherwise not comply with a regimen of SCIT.

Why is SLIT still an off-label treatment in the United States? 

Despite international use and growing use among other U.S. specialties, U.S. allergy leadership’s current view on SLIT suggests limited perspective and interest in researching certain multi-antigen SLIT treatment approaches, though research finds the SLIT mechanism to be both safe and effective. Only single-antigen, standardized dose SLIT tablets have received FDA approval to date.

Multi-Allergen Inhalant Dosing

The appropriate dosing protocol depends on the patient’s history, symptoms, and the number and severity of sensitivities. The starting treatment level is intended to be therapeutic, and is based on the patient’s skin test or specific IgE class results. We recommend using a metered dispenser. Patients are re-evaluated every 3-4 months, and re-tested at 12 month intervals for evidence of reduced skin test or IgE class results at provider’s discretion. 

SLIT Side Effects and Special Considerations

If mouth itching develops, use an antihistamine. Reduce dose, or stay at the same concentration until itching subsides and tolerance increases.

Critical SLIT Attributes

Research supports SLIT’s superior safety profile (see references below). This allows treatment for the widest range of allergy patients including children of all ages. Because treatment is taken at home, SLIT patients report improved adherence (some studies indicate 80-90%), a contrast from the poorer compliance statistics reported for SCIT.


References:

  1. Passalaqua, G., Compalati, E., Canonica, G.W. Sublingual Immunotherapy: Clinical Indications in the WAO- SLIT Position Paper. World Allergy Organization Journal 2010 Jul;3(7):216-219.

  2. Theodoropoulos, D., Morris, M., Morris, D. Emerging Concepts of Sublingual Immunotherapy for Allergy. Drugs of Today 2009, 45(10):737-750.

  3. Bordignon V, Burastero SE. Multiple daily administrations of low-dose sublingual immunotherapy in allergic rhinoconjunctivitis. Annals of Allergy, Asthma & Immunology 2006, 97:158-163.

  4. Cox, L., Li, J.T., Nelson, H., et al. Allergen Immunotherapy: a practice parameter second update. Journal of Allergy & Clinical Immunology. 2007 Sep;120(3Suppl):S25-85.