Allergen Immunotherapy 101

6 min read



Allergy immunotherapy has been clinically practiced for over 100 years. Sublingual immunotherapy (SLIT), in particular, has been utilized since the 1980s. This proactive treatment helps the body develop immunity to an allergen by giving gradually increasing doses of the substance.

What is allergen immunotherapy?

Allergen immunotherapy (AIT) is a treatment that targets the underlying cause of allergies and ultimately leads to immunologic tolerance. By desensitizing the immune system to the allergen, AIT can lead to lifelong symptom relief and/or prevent the disease from progressing. This means preventing the development of asthma in children with allergic rhinoconjunctivitis, and, potentially, also preventing new allergies.¹

Simply put, it is a long-term management plan that will at the very least, make allergies significantly milder and reduce the need for medication, and at the very best, eliminate them.

What is the history of this treatment?

The two most common types of immunotherapy are subcutaneous immunotherapy (SCIT), more commonly referred to as allergy shots, and sublingual immunotherapy (SLIT) given as fast-dissolving tablets or as drops under the tongue, which is what we offer here at Nectar: sublingual allergy drops.

SCIT has been used for over 110 years while SLIT has been in action for over 30. The primary reason for proposing and studying an alternative to allergy shots was to improve patients' safety and convenience.

"Immunotherapy helps the body develop immunity to the allergens, so that you can tolerate them with fewer or no symptoms."

How does allergy immunotherapy work?

Allergen immunotherapy treatments are often conducted in two phases: an initial up-dosing phase, followed by a maintenance phase. In the up-dosing phase, which usually lasts 3 to 6 months, increasing doses of the allergen are given to the patient to slowly build their tolerance.

Then begins the maintenance phase, which is the maximum dose given to the body for the remaining course of the treatment. In the case of SLIT tablets (e.g., Odactra), there is no buildup phase.

The idea with AIT is to regularly expose the body to the allergen to build immunity, decrease sensitivity, and result in fewer or no symptoms.

SCIT is administered via frequent injections, often given 1-2 times per week, while SLIT exposes the body to the allergen orally through daily doses taken under the tongue.

When a person is naturally exposed to their allergens, the body responds with allergic inflammation and symptoms develop almost instantly such as sneezing, itchy eyes, and a runny nose. However, when an allergen is administered as immunotherapy, the immune system responds differently. First, the patient is given almost “100 times the estimated maximal yearly intake through natural exposure” in a single dose, and second, the allergen enters the body differently, either sublingually (under the tongue) or subcutaneously (as an injection under the skin).² These two differences in exposure to the allergen alter the way the body responds and instead induce immunological tolerance to the allergen.

How long does it take to treat allergies?

This isn’t a sprint. It’s a marathon. Generally, patients usually begin to see improvement in symptoms within 4 to 5 months of initiation, and the allergy treatment overall lasts between 3 to 5 years. However, as each patient is different and has a custom immunotherapy treatment plan, the time to symptom improvement may vary. When compared to a lifetime of relief, a few years isn’t too long of a commitment.

Are there side effects?

SCIT may cause some patients to develop swelling at the site of the injection. This can be managed with ice packs or oral antihistamines.

More severe reactions, like anaphylaxis, are uncommon, but patients are still advised to:

- Remain in the doctor's office for at least 30 minutes after each injection.
- Avoid exercising for 1 hour prior to the injection and for at least 2 hours afterward.
- Avoid some heart and blood pressure medications.

SLIT is generally considered much safer but can still have mild side effects including irritation, swelling, itching inside the mouth, or stomach upset. It generally resolves within minutes of taking the dose and becomes less problematic after the first few weeks. Taking an antihistamine beforehand can also help curb the side effects.

What is the societal benefit of allergen immunotherapy?

Allergies are a growing worldwide health issue. According to the World Health Organization, hundreds of millions of people in the world suffer from rhinitis and an estimated 235 million have asthma.

​​The societal cost of allergies is substantial, not only because of how many people suffer from the disease but because of the associated loss of productivity. A U.S. study published in the peer-reviewed journal, Current Medical Research and Opinion, established rhinitis as the most costly disease for American employers.³ This is no surprise when accounting for how allergy symptoms impact sleep and performance at school and work.

Allergen avoidance and medication (i.e. ​​antihistamines, decongestants, and other medications used to control allergy symptoms) can be effective but not for everyone. Only AIT has the potential to modify the disease and offer a truly better quality of life long-term.

Receiving the treatment revives productivity and saves money on OTC medications and visits to general practitioners and specialists. Better still, one of the benefits of treatment is the potential to reduce the risk of asthma development in some patients and the associated costs.

What makes AIT different from other treatment options out there is its capacity to alter the disease for the better. Spending time, effort, and money on this firmly established treatment is a worthwhile investment not only on an individual level but a societal one as well.


¹ Cools, M et al. “Long-term effects of specific immunotherapy, administered during childhood, in asthmatic patients allergic to either house-dust mite or to both house-dust mite and grass pollen.Allergy vol. 55,1 (2000): 69-73. doi:10.1034/j.1398-9995.2000.00191.x

² Lowenstein, Henning. "New and Improved Vaccines for the 1990s." Clinical & Experimental Allergy, May 1991.

³ Lamb, Charles E et al. “Economic impact of workplace productivity losses due to allergic rhinitis compared with select medical conditions in the United States from an employer perspective.Current medical research and opinion vol. 22,6 (2006): 1203-10. doi:10.1185/030079906X112552

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