What Is Allergy Immunotherapy, and Does It Work?

More than 100 million Americans—many who are otherwise healthy—experience allergies to everyday exposures like pollen, mold and pet fur, according to March 2023 data from the Asthma and Allergy Foundation of America. While many of today’s allergy medications are effective in helping manage their allergy symptoms, the strength of these meds is sometimes also their greatest limitation—these drugs treat allergy symptoms, not the allergic reaction itself.

So, that’s the goal for allergy immunotherapy, a rapidly growing field that aims to prevent allergies altogether for permanent relief.

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What is allergy immunotherapy?

At its core, an allergic reaction is a mistake of the immune system, says Manan Shah, MD, ENT, an otolaryngology doctor and co-founder and chief medical officer of Wyndly, a telehealth platform that facilitates at-home allergy immunotherapy treatment.

Here’s what happens: The body identifies something relatively harmless, like pollen, as a potential threat—and releases antibodies to attack it. As these antibodies bind to the pollen, histamine gets released into your system. “Histamine makes your blood vessels get bigger,” Dr. Shah explains. “So your nose gets stuffy, your eyes get watery, [the inflammation] just makes you feel miserable.” Anti-histamine allergy medications bind to the histamine to prevent this reaction from occurring—and while this is effective for many people, it only works as long as the drug is in your system.

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Immunotherapy works more like a vaccine that builds up your tolerance against an allergen over time, Dr. Shah says. “When the human body is exposed to something in small doses, it’s able to become more tolerant,” he explains. “People do this with lifting weights—they expose their muscles to more and more weight, and they’re able to get stronger.”

Allergy immunotherapy is based on the same concept: By exposing someone to progressively greater amounts of an allergen, it safely changes the way your immune system responds. Specifically, “it actually helps you create more antibodies, so when you’re exposed to pollen, a different antibody binds to it, so you never release histamine in the first place.”

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How does allergy immunotherapy treatment work?

Immunotherapy treatment goes back as far as 1900 when a physician named H.H. Curtis treated farmers with hay fever using a whole weed extract. “In these historical days, allergists would actually go out into the fields and collect [plants] and grind it up with a mortar and pestle,” Dr. Shah explains.

Today, some allergists are using FDA-approved allergy extracts that are purified versions of an allergen and can be modified in their concentration level. There are a few methods available to deliver this treatment:

Allergy shots

Formally called subcutaneous (under the skin) injections, allergy shots are administered in a doctor’s office, usually over the course of a three- to five-year period. Treatment plans will vary, but in general, “the most common version is an injection once a week during what’s called a build-up phase,” says Stephan Canfield, MD, a board-certified allergist/immunologist and assistant professor of medicine at Columbia University Irving Medical Center. “We start with very, very low dilutions—almost water—and then every week we increase the dose a little bit.”

Some patients can complete this build-up phase in about a month, while it may take six to eight months for others. “Then we get to a place that we call the maintenance dose, a dose that’s high enough that we don’t have to build any more [tolerance], and that’s a monthly injection,” Dr. Canfield says.

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Oral tablets

Sublingual (under-the-tongue) tablets are also available—and their main benefit is that you can take them at home. But “the main limitation is that there are only three allergen tablets that have been approved by the FDA: Grass pollen, ragweed pollen, and dust mites,” Dr. Canfield says. “So at the moment in the US, oral [tablet] immunotherapy is typically for what we call a mono allergy—having only one allergy—and unfortunately, that’s relatively rare.”

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Oral drops

Like oral tablets, sublingual immunotherapy drops also require no in-office treatment. But, explains Dr. Shah, because these formulations use the same raw materials as allergy shots, they address a broader range of airborne allergens and doctors can customize a mixture to your needs. “Some patients notice that within four to six weeks their symptoms improve,” he says. “But for the majority of patients, around three to six months is when they really start to feel a lot better.”

Most patients using sublingual immunotherapy undergo treatment for about three years.

How effective is allergy immunotherapy?

“Across immunotherapy, the success rate is about 80% to 85%—that’s including shots and sublingual [treatment],” Dr. Shah says. The effects are also long-lasting after you complete your course. “There are clinical studies that follow up with people eight years after treatment, and they continue to feel better,” he says. “In general, we tell people this is the way to fix your allergies for life.”

Allergy immunotherapy is also a very safe treatment available to almost anyone with allergic rhinitis, allergic asthma, eye allergies, or a stinging insect allergy (though it’s not generally recommended for children under age five). “One of the most common reasons I see people go this route is that they’ve reached the end of their rope,” Dr. Canfield says. “Their symptoms are not just not controlled [with medication].” However, he says he also encounters a number of patients who simply aren’t happy with the idea of taking allergy medication for the rest of their lives. “They would much rather get to the bottom of [the issue], go for something that’s a cure.”

One big limitation of immunotherapy is that it doesn’t currently address food allergies—but this is an emerging field with a lot of work going on, according to Dr. Canfield. For instance, there’s now a treatment called Palforzia that is an in-office desensitization protocol for people with peanut allergy. “Unfortunately, that doesn’t mean your kid can start eating peanut butter cups after treatment,” Dr. Shah says. “But we can get your kid to the point where if they’re eating lunch at a cafeteria and there’s peanut contamination, they’re not going to have a life-threatening reaction.”

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