Most patients’ experiences with sublingual immunotherapy (SLIT) drops is that they are easy to take and without significant side effects. However, like any treatment, there is a potential for adverse effects in certain circumstances, and it is important to be able to recognize them and know what to do. The most common side effects of SLIT are mild local reactions in the mouth such as tingling, a sensation of warmth, or itching. These symptoms tend to occur more often during the beginning of your treatment program or just after a dose increase during the buildup phase, and they tend to resolve within a couple minutes of a dose and stop occurring altogether within a few days or a week. For these symptoms, no medical intervention or dose adjustment is typically needed.

In patients with a history of eczema at any time, an eczema flare can also occur, especially at the initiation of treatment, during an illness, or during an updose. In the long run, SLIT treatment significantly helps control eczema, but it may also contribute to some (usually mild) flares, especially at the beginning, given the complexity of the eczema immunologic process.

Other adverse effects can occur but are more rare, and these can in theory be any type of allergic reaction since with immunotherapy treatment comes exposure to your allergens (albeit in a highly controlled way). Sneezing, increased mucus production in the nose and mouth, nasal congestion, mild asthma symptoms, hives, or a stomach ache have occasionally been reported in studies. Anaphylaxis is not a typical adverse effect concern with sublingual immunotherapy drops, especially when treatment is prescribed and managed by an allergist with the appropriate related skills and expertise and when using a long-term treatment method.