Sublingual Immunotherapy for Environmental Allergies

Lilian White, MD
Posted on September 15, 2025

Allergic rhinitis is common, affecting approximately 15% to 30% of the population in the United States. It is the most common cause of work absenteeism. The diagnosis and treatment of allergic rhinitis may be based on history and physical examination alone, without additional testing.

First-line treatment of allergic rhinitis primarily comprises intranasal corticosteroids. Allergy testing is recommended when the diagnosis is uncertain or the patient does not respond to first-line treatment. Immunotherapy may be offered to patients with moderate or severe symptoms of allergic rhinitis that do not respond to initial treatment, those who do not tolerate medications for allergies, those who wish to avoid long-term medication use, or in those with allergic asthma. Immunotherapy generally comprises gradually exposing the patient to increasing concentrations of allergen to build immune tolerance. Options include subcutaneous immunotherapy (SCIT; ie, allergy shots) and sublingual immunotherapy (SLIT).

SCIT has historically been and continues to be the primary option for immunotherapy for environmental allergens, but SLIT is growing in popularity for its ease of use, cost, and safety. The US Food and Drug Administration (FDA) has currently approved several sublingual tablets for the treatment of pollen, grass, and dust-mite allergies. Sublingual drops show some promise for treatment, but, although they are used in other countries with FDA-approved allergens, they are not currently approved by the FDA.

SLIT is considered a little safer compared with SCIT. It is rare for SCIT to result in complications leading to death (eg, anaphylaxis), but SLIT has yet to be associated with any deaths. Treatment appears to be similarly effective for patients with allergic reactions to one vs multiple allergens. Additionally, treatment for one major allergen appears to reduce the patient’s reactions to other cross-reactive allergens. SLIT is at least as effective or more compared with pharmacotherapy alone, but it results in significantly more cost savings (estimated 80%). Both SCIT and SLIT reduce the need for medication to treat symptoms. Children tend to have higher response rates compared with adults. Beneficial effects of SLIT have been found to persist for as long as 7 years after treatment. SLIT is considered more cost effective than SCIT when indirect costs such as patient travel and missed time from work or school for SCIT are considered.

Contraindications to SLIT include severe or uncontrolled asthma, pregnancy, or inability to tolerate epinephrine injection. Relative contraindications include a patient history of anaphylaxis, immunosuppression, and eosinophilic esophagitis. Only about 5% of patients discontinue SLIT due to adverse effects, which include oral or ear pruritus, mouth edema, and throat irritation. Initiation of treatment during the flowering season may increase the risk of adverse effects.

For safety, it is recommended to monitor patients for 30 minutes after the initial dose in the office. All patients should carry an auto-injectable epinephrine pen. Immunotherapy is not currently recommended for food allergies because of risk of severe adverse effects. Treatment with immunotherapy is recommended for at least 3 years.