Everything You Need to Know About Immunotherapy for Allergies

Allergy Shots, Sublingual, and Oral Therapies

Immunotherapy is one approach to treating allergies. Allergy symptoms happen when the immune system overreacts to a foreign substance—an allergen—causing symptoms like runny nose and bloodshot eyes (allergic rhinitis) or worsened asthma (allergic asthma).

This article discusses different types of immunotherapy, including allergy shots, sublingual immunotherapy, and oral immunotherapy. It also discusses potential benefits and side effects, treatment schedules, and insurance coverage.

Closeup image of a gloved hand holding a vial filled with clear liquid.

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How Does Immunotherapy for Allergies Work?

In contrast to allergy treatments, such as antihistamines that temporarily reduce symptoms, immunotherapy gradually changes your immune system’s response to the foreign substance over time. Eventually, your immune system cells won’t react to the allergen in the same unhelpful way, so symptoms no longer occur.

All types of immunotherapy for allergies work on the same principle. Over time, you are exposed to more significant amounts of an allergen. The idea is that eventually, your immune system learns to adapt to the allergen, which reduces or eliminates the allergic reaction and its symptoms.

Before treatment, a healthcare provider does an allergy test to determine what substances you are allergic to, like grass, pollen, animal dander, insect stings, or mold. Depending on your bodily response, you get immunotherapy geared at one or more of those specific substances, so you’ll gradually become less reactive to them.

Types of Immunotherapy for Allergies

Currently, the three major immunotherapy approaches for allergies are:

  • Allergy shots, also called subcutaneous immunotherapy (SCIT))Sublingual immunotherapy
  • Oral therapy

Allergy Shots

Allergy shots are the oldest and most established form of allergy immunotherapy. A provider administers an injection beneath your skin. The injection contains a small amount of the substance you are allergic to, such as pollen, mixed with a delivery liquid. Gradually, the medical provider increases the concentration of the allergen over time.

Sublingual Immunotherapy

Tablet sublingual immunotherapy (SLIT) is another immunotherapy option. You place a tablet under your tongue for several minutes until it dissolves.

Currently, the only sublingual immunotherapy allergen treatment options approved by the Food and Drug Administration (FDA) are for ragweed, grass, and dust mites. So if you are allergic to other substances, it is not a good option.

Allergy drops are another option in this category. One advantage of allergy drops is that a healthcare provider has more allergen options and can formulate a blend for each individual based on their needs. Allergy drops are not FDA-approved in the United States but are sometimes used off-label.

Allergy Shots vs. Sublingual Therapy

Although rare, allergy shots have a greater risk of causing severe side effects compared to sublingual immunotherapy. However, it’s unclear if sublingual therapy is as effective as allergy shots.

Food Allergy Immunotherapy

Oral immunotherapy to treat food allergies is the least established form of immunotherapy. It addresses food allergy symptoms, not allergies from airborne allergens that trigger allergic asthma or rhinitis.

The theory behind oral immunotherapy is similar to other forms of immunotherapy in that a person ingests more significant amounts of an allergen over time to adjust the immune response.

The only food allergy immunotherapy specifically approved by the FDA is Palforzia, a formulation of peanut powder. Some healthcare providers use this approach with eggs and other allergens, although the FDA doesn’t approve a specific formulation.

However, there isn’t a medical consensus about whether food allergy immunotherapy or avoidance is a better approach for most people. Currently, oral immunotherapy may not work as well as other forms of immunotherapy.

Who’s Immunotherapy Right For?

As with any other medical therapy, you’ll have to work with a healthcare provider and weigh the risks and benefits to determine if immunotherapy is right for you.

Potential Benefits of Immunotherapy

You may want to consider immunotherapy if your allergies are moderate to severe. Immunotherapy may be an option if you are trying to avoid your triggers but are unsatisfied with your allergy medication.

Potential benefits of immunotherapy include the following:

  • Improved quality of life: Immunotherapy may benefit you if your allergic rhinitis or asthma interferes with your quality of life. It may also be helpful for people with severe eczema, although it’s used less often.
  • Decreased symptoms, medications, costs, and side effects: Once you’ve completed your immunotherapy regimen, your symptoms might be significantly reduced. You may be able to reduce or eliminate medications, resulting in decreased costs and side effects.
  • Reduced risk of severe reactions: People with a history of severe allergic reactions, such as difficulty breathing from an insect sting or particular food, may also find reducing their risk of dangerous reactions empowering.

Effectiveness of Immunotherapy for Allergies

Most people who complete a full course of allergy immunotherapy eventually see its benefits lasting eight to 10 years or longer after completing a course of therapy.

People Who May Need to Avoid Immunotherapy

Immunotherapy isn’t the right choice for everyone. For example, it might not be the right choice if any of the following is part of the clinical context:

  • Pregnancy
  • Young people or older adults (under 5 or over 65, although it can vary)
  • Uncontrolled asthma
  • Cancer
  • Beta-blocker medication such as Lopressor (metoprolol)

Immunotherapy is not the right treatment for people with skin allergic reactions, such as after touching poison ivy. Additionally, it is typically not suitable for people who get intensely red, itchy skin (urticaria) or for people who get extreme swelling around the throat (angioedema) from allergies.

How Often Do You Get Immunotherapy Treatments?

The frequency of immunotherapy treatment varies based on your clinician’s approach, personal preferences, and the type of immunotherapy you’ll receive.

For allergy shots, you typically receive weekly shots for about four to six months in the buildup phase and then a shot every month or two for the next three to five years. However, some people follow rushed schedules, receiving shots more frequently for a limited period.

For sublingual treatment, the approach may vary based on the type you receive, such as ragweed vs. grass or dust mites. You might take them three days a week or up to every day for three to five years, with some types taken only seasonally.

People taking oral therapy will take it daily at first, followed by less frequent dosing. The maintenance phase may last for years or continue indefinitely.

How Soon Do You See Results?

It’s important to be patient with immunotherapy. Some people start to see results in the initial buildup phase. For others, it might take a year or even longer to notice symptom improvement.

Side Effects of Immunotherapy

Potential side effects of immunotherapy vary based on the type you receive.

Allergy Shot Side Effects

Some common side effects of allergy shots are mild swelling, itching, and redness at the injection site. After your initial shots, you’ll understand what to expect.

Less common are serious side effects that might affect other body areas, like itchy red bumps on the skin or wheezing.

Most concerning is a very rare but potentially life-threatening problem called anaphylaxis, which can cause symptoms including:

  • Swelling in your throat
  • Very low blood pressure
  • Rash
  • Vomiting
  • Trouble breathing

Sublingual Immunotherapy

Unlike allergy shots, sublingual immunotherapy doesn’t carry a risk of severe reactions like anaphylaxis. However, it may cause issues such as itching or burning of the mouth. Less commonly, it causes symptoms such as:

  • Nausea
  • Belly pain
  • Diarrhea

Risks in Uncontrolled Asthma

People with uncontrolled asthma may run the risk of having anaphylaxis or a severe asthma attack if they start immunotherapy. A better approach is first to decrease asthma symptoms using medical therapies. From there, many people with allergic asthma can safely respond to immunotherapy.

Oral Immunotherapy

Oral immunotherapy can cause side effects such as:

  • Stomach pain
  • Itching or burning in the mouth
  • Runny nose
  • Wheezing

Anaphylaxis is rare but possible with oral immunotherapy.

Does Insurance Cover Immunotherapy for Allergies?

Many insurance plans cover allergy shots but usually require a co-pay. In addition to the shot itself, you may need to pay for having the shot given to you in a clinic. These costs can add up because allergy shots are given over a long period.

Some insurance plans cover sublingual tablet immunotherapy, but some do not. Also, because allergy drops are not FDA-approved, they are not covered by insurance.

With the possible exception of oral peanut immunotherapy, insurance is less likely to cover oral immunotherapy approaches.

What to Expect During Immunotherapy

There isn’t anything you need to do to prepare for immunotherapy other than your initial allergy testing and deciding on a treatment approach with a healthcare provider. You can eat and drink normally before and after your treatment.

One of the advantages of sublingual treatment over allergy shots is that allergy shots need to be given in a healthcare setting. That’s partly because they carry a greater risk of side effects so you may require more monitoring compared to sublingual treatment approaches.

When to Seek Emergency Care

Seek emergency care for any of the following or for other severe symptoms which may indicate anaphylaxis:

  • Wheezing or difficulty breathing
  • Swelling of the lips, mouth, throat, or tongue
  • Trouble swallowing or speaking
  • Raised itchy bumps on the skin
  • Chest pain
  • Severe stomach pain

If you are receiving allergy shots, a healthcare provider will be prepared to administer epinephrine in the rare event that you experience any potentially life-threatening symptoms. You can also administer your own epinephrine via an EpiPen at any signs of a severe reaction.

Summary

Immunotherapy is one treatment approach for allergies, such as those that cause symptoms of allergic rhinitis, allergic asthma, or symptoms of food allergies. Unlike medications to treat symptoms, immunotherapy gets at the root cause to reeducate your immune system to tolerate allergens better. Most people get some symptom relief, but treatment takes a few years.

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By Ruth Jessen Hickman, MD
Ruth Jessen Hickman, MD, is a freelance medical and health writer and published book author.