9 Things You Need to Know About Allergy Shots

Allergy shots work by exposing patients to tiny amounts of whatever it is they’re allergic to. The amount of allergen in each injection increases gradually over time so the body can build up a tolerance.

“It changes the person’s immune system from having a bad reaction to pretty much ignoring the allergen,” says Dr. Dziadzio. “For some people, it decreases their allergies enough so they can come off medicine entirely, and for some it helps their medicines be more effective.”

But because allergens are involved, reactions to the shots themselves are possible. These can range from swelling and itching at the injection site (usually the arm) to sneezing and a runny nose, to, in rare cases, anaphylactic shock. That’s why it’s recommended that patients stay at their doctor’s office for 30 minutes after each shot so they can be monitored and treated for reactions if they do occur.

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Allergy shots can be effective for people with hay fever and other seasonal allergies, but they can also work for year-round indoor allergies—like mold, dust mites, and animal dander—and allergies to insect bites or stings. (Unfortunately, they don’t seem to work for food allergies.)

“In the case of stinging insects, the shots can be close to curative,” says Dr. Dziadzio. “That’s the one time I really push people to get the shots no matter what, because it’s such a dangerous allergy.” Allergy shots may also be a good choice for people who don’t like taking medications or can’t (or don’t want to) avoid the thing they're allergic to—like a pet or the great outdoors.

Allergy shots are given in two phases. In the “build-up” phase, you’ll need a shot once or twice a week for about three to six months. After that, you’ll enter the “maintenance” phase and receive them less often—about once or twice a month, for several years.

Sticking to this schedule is important, for the shots' effectiveness and to reduce your chances of having a bad reaction. “For some people it’s absolutely worth it, but some people just don’t have that time to spare,” says Dr. Dziadzio. And while the shots themselves only take a minute, you probably will have to wait those 30 minutes in your doctor’s office after each one.

Taking an oral antihistamine (like Benadryl or Claritin) before each shot can help reduce side effects and reactions. “We really encourage patients to take them beforehand, especially as they get closer to their maintenance dose and their local reactions [on their arms] can get pretty bad,” says Dr. Dziadzio.

And if that’s not enough reason to pop a pill beforehand, some research even suggests that pre-treatment with an antihistamine during the build-up phase of allergy shots can improve the shots’ effectiveness too.

Allergy shots aren’t a quick fix: While some people may start to feel better during the build-up phase of their treatment, most people won’t experience noticeable improvement until they’ve been in the maintenance phase for six to 18 months, says Dr. Dziadzio.

In fact, a 2017 British study found that it took three full years for allergy shots for hay fever to be more effective than placebo shots. The maintenance phase for most allergy shots is usually continued for three to five years. Some patients experience long-lasting relief after that, and some may need continued treatment.

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Most adults—and children ages 5 and up—can get allergy shots. But if you or your child has severe, uncontrolled asthma, your doctor may recommend against them. “In our practice, if a patient’s asthma is flaring or even if they’re sick, we generally wait to give the shot until they’re feeling better,” says Dr. Dziadzio.

Women who become pregnant while in the maintenance phase of allergy shots can continue their treatment. (Research even suggests that immunotherapy before or during pregnancy may decrease babies’ chances of developing allergies!) But women shouldn’t start allergy shots for the first time, or increase their dosage, while pregnant.

Certain medicines, like beta blockers, can reduce the effectiveness of epinephrine—the lifesaving drug used to treat anaphylactic shock. Because anaphylaxis is a rare but serious risk for people getting allergy shots, they may not be recommended for people who take these drugs.

When people think of allergy symptoms, they generally think of itchy eyes and a stuffy or runny nose, or, in worse-case scenarios, anaphylactic shock. And while allergy shots can help prevent all of those, they can also help with related conditions, as well.

If you have asthma, getting your allergies under control may also help reduce flare-ups, improve your breathing, and reduce your need for medications. Eczema, an inflammatory skin condition, is often associated with (and can be made worse by) environmental allergies.

It’s not just physical symptoms that can get better with allergy shots; mental state can improve, as well—especially if severe allergies have really taken a toll on your health and happiness.

This may be especially true for insect allergies, a condition that can cause serious distress and affect a person’s ability to enjoy the outdoors. One 2014 study found that patients with insect-venom allergies who received immunotherapy not only had a lower risk of anaphylaxis and death than those who didn’t, but also had lower anxiety and depression scores.

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For people who hate shots or can’t keep up with their intensive schedule, sub-lingual therapy may be another option. This type of immunotherapy is delivered in daily tablets that dissolve under the tongue, and only the first few doses need to be taken with a doctor present.

Sub-lingual therapies are currently on the market for grass pollen (for children and adults) and for ragweed pollen (for adults only). Some allergy practices will also administer liquid drops under-the-tongue to treat other types of allergies, although these treatments are not FDA-approved.

This post was originally published on March 30, 2017 and updated for accuracy.