What Is Sublingual Immunotherapy?

Sublingual immunotherapy, which is abbreviated as SLIT, is an alternative treatment method for allergies without the use of injections. SLIT involves the administration of allergens in small doses to patients to boost their tolerance to the chemicals, thereby reducing their symptoms. 

Allergic rhinitis, also known as hay fever, is a major inflammatory disease that causes runny and itchy nose, sneezing, watery and itchy eyes, and nasal congestion. For years, nasal corticosteroids and antihistamines have been used to relieve its symptoms. However, the medications have only been seen to temporarily reduce the symptoms.

The most effective method you can use for the treatment of severe allergies such as rhinitis is sublingual immunotherapy. It has been recently approved in the United States. Instead of using allergic tablets and shots, SLIT uses allergens in liquid and tablet forms. They are usually administered under the tongue on a daily basis.

Mechanism of Action for SLIT

Sublingual immunotherapy is a procedure that enables the specific antigens present in the mouth to induce tolerance to the allergen. The dendritic cells found on the mucosa takes the antigen and then brings it to the basal lamina, where the antigen is then presented to the T-cells, which induce an effector response.

Antigens can also move to the regional lymph nodes, where the formation of regulatory T cell and native T cells are enabled. Long-term changes after a sublingual immunotherapy include a reduced number of mast cells and mast cell sensitivity, as well as the production of Immunoglobulin E (IgE) by the B-cells. As the allergic condition improves, the symptoms improve as well. As multiple mechanisms are used in a sublingual immunotherapy, different outcomes are observed in different patients, which means that the effectiveness of SLIT depends solely on dosage, frequency, and antigen of choice.

How is it administered?

Before the administration of sublingual immunotherapy drops, the patient should undergo an allergy test to know how sensitive he or she is. Once the test is complete, an allergen is prepared in the form of a tablet or drop before being prescribed. The patient is then advised to put it under the tongue for about two minutes and then swallow it. The procedure is then repeated three times a day and then once daily.

Is sublingual immunotherapy different from allergy shots?

Allergy treatments may use allergy shots, which are also known as subcutaneous immunotherapy (SCIT) that requires two phases. Phase 1 uses frequent injections with an increasing amount of the allergen extract. The first phase is then followed by a maintenance phase, where you are given injections once a month. Allergy shots can sometimes be effective in the treatment of allergies, but the schedule of shot administration is very hard to follow or maintain.

On the other hand, SLIT is a therapy that can be administered at home with no buildup phase required, which means that there are no extra trips to the doctor like in SCIT. The tablets used in SLIT are safer and can be used at home without being watched by your doctor.

Considerations When Prescribing Sublingual Immunotherapy

Below are some of the considerations that patients should put in place when deciding on taking sublingual immunotherapy prescriptions:

• Safety - The main side effect of SLIT is oral itching during the treatment. The less common side effects include gastrointestinal and esophageal discomfort. By temporary reducing the dosage of sublingual immunotherapy drugs, you can limit or reduce the adverse effects of the drugs. However, there have been no life-threatening conditions that are associated with SLIT.
• Dose and frequency - The approach for sublingual immunotherapy should be individualized for every person. The treatment's effectiveness is determined by the frequency of administration, antigen of choice, and dosage. The amount of antigen used is usually determined through the patients’ test results. As you progress with the treatment, the antigen dosage is adjusted. The normal drug frequency is a low-dose antigen taken 2-3 times a day at home.
• Patient selection - Every patient who needs a sublingual immunotherapy should undergo an evaluation with an allergy specialist. It is also important for the doctor to know the patients who should be referred. They include:
  • Patients with asthma - SLIT can help desensitize the allergic triggers, which can help reduce the need for asthma medications.
  • Infants and children - An allergy evaluation is very important in children with recurring otitis and eczema. These conditions have an underlying allergic etiology.
  • Patients with chronic sinusitis - Mold sensitivities and chronic sinusitis are two linked conditions. Treating an underlying allergic condition can also help treat sinus infections.
  • Patients with mild allergic conditions - Some allergies are treated differently, but SLIT can help the most sensitive patients become tolerable to certain allergies.
  • Highly-sensitive patients - SLIT is very important for patients who are unable to take allergy shots, which include patients who do not take injections, people with a history of systemic reactions, people living in remote areas, and patients who cannot travel.
  • Patients with multiple allergies - SLIT can help ease allergies caused by pollens, pet dander, molds, and dust.
• Cost- Most insurance plans do not cover the expenses of SLIT. SLIT is mostly considered as an economical choice compared to co-pay allergy shots.

Advantages of SLIT

The advantages of SLIT include:

• safe to use in hospitals and at home
• saves a lot of time and money one would use for clinic visits
• an easier and tolerable procedure as it doesn’t use needles to administer the drugs
• a good procedure for daily travelers
• more child-friendly and is always safe for infants
• proven to be effective in reducing eczema, childhood asthma, and chronic ear infections
• aimed to treat a broad range of allergic diseases and also prevent new allergies
• achieves a long-term alteration of the body's immune response to many allergens
• controls asthma and also prevents its development

Disadvantages of SLIT

• not covered by many insurance companies as they term it as an experimental procedure
• more expensive compared to some of the lifetime allergy medications
• a slower procedure compared to allergy shots since it takes a longer time for someone to feel better with the drops
• not FDA-approved

Bottom Line

Sublingual immunotherapy has been considered a relatively effective treatment for rhinitis and asthma due to allergens. Evidence has also emerged that SLIT can also treat red and itchy eyes caused by hay fever.