Allergies happen when your immune system overreacts to harmless substances called allergens. Allergy desensitization shots make your body less likely to react to allergen.
Allergies happen when your immune system overreacts to harmless substances called allergens. Allergy desensitization shots make your body less likely to react to allergen.

Allergies happen when your immune system overreacts to harmless substances called allergens. When you come into contact with an allergen, your body makes antibodies and releases chemicals like histamines. These antibodies and chemicals cause inflammation and lead to symptoms like sneezing, itchy, red eyes, hives, and runny nose

Normally, allergy treatment involves avoiding allergens, and taking medications like antihistamines, decongestants, or steroids to reduce inflammation and symptoms. 

Sometimes, allergies can last a long time or interfere with your life, though. Moreover, some people have severe allergies that cause anaphylaxis, which can be life-threatening.

Allergy desensitization shots can be helpful for severe allergies or in cases where other treatments don’t work. They are considered a disease-modifying treatment because they can make some allergies better. The effects can last long after the treatment stops, but it’s not necessarily a cure.  

What medication is used for allergy shots?

Allergy desensitization shots are made of allergen proteins mixed with preservatives and solvents. This is called an extract. Your doctor will give you the extract that matches your allergy. If you’re allergic to cat dander, you will get the cat dander extract, for example. 

Over time, your doctor will slowly increase the amount of allergen in your shots. The gradual buildup changes your immune system and desensitizes it to the allergen. Your body gets used to the allergen, and you become less likely to react to it. 

There are also other forms of desensitization treatment called sublingual immunotherapy. These are drops or tablets of extract that you put under your tongue for 1 to 2 minutes and then swallow.

What allergies can you get shots for?

Not all types of allergies can be treated with allergy shots. These shots are only helpful for IgE-mediated allergies, which cause a quick reaction throughout your whole body within minutes or hours. 

Additionally, allergy shots can only help specific allergies, including seasonal, indoor, and insects. These include allergies to:

  • Dust mites
  • Grass pollen
  • Tree pollen
  • Weed pollen
  • Cat dander
  • Dog dander
  • Mold
  • Cockroaches
  • Bees
  • Wasps
  • Hornets
  • Yellow jackets

Your doctor might prescribe allergy shots if:

  • You have moderate to severe symptoms that last for months
  • Other treatments aren’t helping
  • You react to medications
  • You try to control exposure, but your symptoms still last
  • You want to stop taking long-term allergy medications
  • You’re allergic to insect stings

How long does it take for allergy shots to work?

Allergy shots take time. The process usually involves 2 phases over 3 to 5 years and includes a buildup phase and a maintenance phase.

The buildup phase takes 3 to 6 months. You get 1 to 3 shots a week, starting with the weakest extract and slowly building up until you reach the strongest dose. Once you reach this stage, you’ll move to the maintenance phase, where you’ll receive doses once a month for 3 to 5 years. 

Sometimes, your doctor can speed up the process and perform rush immunotherapy. In a rush process, you get several shots in one visit. This can be helpful if you have severe allergies and need to get relief faster, but you face a higher chance of having a severe allergic reaction

Do allergy shots have side effects?

You get a small amount of something you’re allergic to every time you get a shot. This means that there’s a chance that you’ll have an allergic reaction. Small reactions at the injection site are common and mild, while more severe full body reactions are rare. 

Common side effects include:

Serious reactions can include:

Severe reactions are more likely to happen if you have a cough, are sick, or are wheezing before you get a shot. Some medications like beta-blockers might also cause complications and make it harder to treat reactions. If you take these, your doctor might first adjust your medications before starting shots. 

Most reactions happen within 30 minutes of getting the shot. You’ll need to sit in your doctor’s office or the clinic for those 30 minutes to make sure you don’t react. 

Are allergy shots an underused treatment?

Some research suggests that allergy shots are an underused treatment, but allergy shots can only be used for certain allergies. They can stop you from getting new allergies or experiencing asthma, and they can make your symptoms better, but they’re not a definitive cure. Your doctor might only recommend shots if nothing else helps. 

If you’re struggling with your allergies, talk to your doctor about whether allergy shots can help you. 

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Common Allergies: Symptoms and Signs See Slideshow

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Medically Reviewed on 11/15/2021
References
SOURCES:

Allergy, Asthma & Clinical Immunology: "Allergen-specific immunotherapy."

American College of Allergy, Asthma, & Immunology: "Allergy Immunotherapy."

Children’s Hospital of Philadelphia: "Allergen Immunotherapy," "IgE-Mediated Food Allergies."

InformedHealth.org, "Hay fever: Allergen-specific immunotherapy (desensitization) in the treatment of allergies," Institute for Quality and Efficiency in Health Care, 2006.

Mayo Clinic: "Allergies," "Allergy shots."

National Health Service: "Allergies—Treatment."

Persaud, Y., Memon, R., Savliwala, M. StatPearls, "Allergy Immunotherapy," StatPearls Publishing, 2021.