Sublingual immunotherapy is one of the lesser known forms of treatment for allergies in the U.S. Most allergies are treated with a combination of trigger avoidance and antihistamines of some type. And for many people with allergies, this is an effective approach to treatment.
Unfortunately, some of us have more severe allergies that don't respond adequately to that approach. In those cases, an alternative may be to attempt to lessen the sensitivity to the things that act as your allergens.
The most common approach is allergy shots, or subcutaneous immunotherapy. In this approach an allergy specialist, called an allergist, tests you extensively to identify your unique triggers and your level of sensitivity to them. Then the doctor develops a specialized serum for you that is given in shot form over a long period of time (usually once a week for up to two years) in doses that go from very dilute to gradually stronger and stronger, until your body has been desensitized to the allergens in the serum.
It can be very effective, though it doesn't work for everyone. And allergy shots can be risky, as they can trigger an allergic reaction called anaphylaxis. They must be administered in a doctor's office by a healthcare professional, so that can also become costly, especially if you don't have insurance.
An alternative is something called sublingual immunotherapy (or SLIT for short), often called allergy drops, that you take by mouth. The idea is the same, but it's less invasive, can be done at home and has much less risk of side effects. Unfortunately, SLIT has not been officially approved for use in the U.S., despite the fact that it has been mainstream treatment in many parts of Europe for some time now.
Dr. James Thompson did a great review of Sublingual Immunotherapy and Oral Immunotherapy: Are WE There Yet? a couple of years ago, that is still a solid reference.
Today, I thought I'd answer some common questions about SLIT.
1. What is SLIT? Sublingual immunotherapy is serum containing tiny amounts of allergens that you are allergic to. You take these drops under the tongue (sublingual). The aim is to lessen your severity to these allergens over time by constantly exposing you to them in safe amounts.
2. Is SLIT safe? The risk of side effects has always been felt to be low with SLIT, but a recent review of the literature published in the Cochrane Review (a well-regarded scientific publication) upheld these findings. SLIT can be used by both adults and children in your own home. In addition, the World Health Organization has come out and endorsed sublingual immunotherapy as a recommended alternative to allergy shots.
3. Does SLIT really work? Studies have suggested that it does work, especially when drops are taken for 3 to 5 years, minimum, to build immunity. And SLIT has been used around the world for more than 60 years. However, the scientific data is not all completely reliable and there has often been no standardization of factors used in the research. So more studies are probably needed to establish unquestionable reliability.