Services

What is Sublingual Immunotherapy?

What is Sublingual Immunotherapy?

Sublingual immunotherapy, or SLIT, is a form of immunotherapy that involves putting drops of allergen extracts under the tongue. Many people refer to this process as "allergy drops," and it is an alternative treatment for allergy shots. This form of immunotherapy has been used for years in Europe, and recently has had increased interest in the United States. However, it is not approved by the Food and Drug Administration (FDA) in the United States.

SLIT is usually delivered by way of drops of allergen extract placed under the tongue, then either swallowed or spat out. Most studies have looked at swallowing the extract, which seems to work better. Immunotherapy by the oral route (swallowed and not kept under the tongue for any period of time), causes too many gastrointestinal side effects (nausea, vomiting, diarrhea), and therefore is not used. Generally, slit is administered daily, or multiple times per week, over a period of years. Most patients are able to self-administer SLIT at home. Studies have looked at giving SLIT before a pollen season, during a pollen season, both, or year-round. It is not yet known what the best dosing regimen is for SLIT.

How Does SLIT Work?

The immune system of the gastrointestinal tract tends to "tolerate" foreign substances, meaning that it does not respond in an over-active way to swallowed material. This makes sense; otherwise the body would over-react to anything swallowed, including food. When SLIT is administered into the gastrointestinal tract, the immune system tolerates the allergen, instead of the over-reactivity of the immune system, as with allergic disease. This results in less allergy symptoms when the body is exposed to the allergy source, such as airborne pollen or pet dander.

What is the Safety of SLIT?

Over the past 10 year, the safety of SLIT has been well documented. Serious and fatal reactions to SLIT have not been reported to date. Mild side effects, such as an itchy mouth, occur in the majority of people, and moderate side effects have been documented (1 in about every 12, 000 doses), including:

  • lip, mouth and tongue irritation
  • eye itching, redness and swelling
  • nausea, vomiting, abdominal cramping and diarrhea
  • sneezing, nasal itching and congestion
  • asthma symptoms
  • urticaria (hives) and angioedema (tissue swelling)

How Well Does SLIT Work?

SLIT appears to be effective in the treatment of allergic rhinitis, allergic conjunctivitis and, to a lesser degree, allergic asthma. While most studies on SLIT do show benefit in the treatment of allergic disease, the results are somewhat inconsistent, with up to one-third of studies showing no benefit over placebo treatment.

Who Could (or Should) receive SLIT?

People with documented allergic disease (allergic rhinitis, allergic conjunctivitis and/or allergic asthma) by allergy testing may be considered for SLIT. Young children have been shown to tolerate and benefit from SLIT, as have older adults. Pregnant women, as is considered the general rule of thumb for allergy shots, can continue SLIT during pregnancy, but should not start the therapy while pregnant.

Some people may be given a choice between allergy drops and traditional allergy shots. Here are some comparison points between the two different therapies to consider when making a decision:

How Long Does it Take For Shots or Drops to Start Working?

Allergy shots often start working within 3 to 6 months, but definitely within 12 months, depending on how often shots are given. Some studies show that allergy drops start working within 8 weeks of therapy; other studies show benefit may take 1 to 2 years to occur.

How Often are Shots or Drops Taken?

Shots are administered in an allergy office once to twice a week for 3 to 6 months; then once to twice a month for 3 to 5 years total. Drops are self-administered once daily under the tongue at home, most often for 3 to 5 years total.

Which Therapy is Safer - Shots or Drops?

Allergy shots are safe, but need to be given under physician supervision. Patients receiving allergy shots then need to be monitored for 20 to 30 minutes, given the small chance of a serious allergic reaction occurring. Allergy drops are extremely safe - no fatal reactions have ever been reported, although severe reactions have rarely occurred. Allergy drops can be self-administered at home without direct medical supervision.

Which Therapy Works Better - Shots or Drops?

Studies suggest that allergy shots probably work about twice as well as allergy drops.

How Much Do the Different Therapies Cost?

Most medical insurance companies cover a significant amount of the costs of allergy shots, although co-payments and annual deductibles apply. Since allergy drops are not FDA approved, they are not covered by insurance. However, the cost of allergy drops may be offset by savings in terms of not having to spend time and travel costs to a physician's office to receive allergy shots.