(MayoClinic.com) Getting monthly allergy shots certainly isn't your idea of fun — much less your child's. But it might be a worthwhile investment in the long run. Successful treatment with allergy shots generally requires three to five years of regular injections. But, allergy shots can provide relief from symptoms that may continue after treatment is complete.

Allergy shots may offer the best relief if you have persistent allergies that don't respond to medication or if the side effects of allergy medication are intolerable. In children, allergy shots can reduce asthma symptoms and may even play a role in preventing asthma in children who have hay fever.

Allergy shots are a form of treatment called immunotherapy. Each shot contains a tiny amount of the substances that trigger allergic reactions (allergens). Allergy shots contain just enough allergens to stimulate your immune system — but not enough to cause a full-blown allergic reaction. Over time, your doctor will increase the dose of allergy-causing substances in each shot. This helps get your body accustomed (desensitized) to the allergens. Your immune system will build up a tolerance to the allergens, and allergy symptoms will diminish over time.

To be effective, allergy shots are given on a schedule that involves two phases:

• The buildup phase generally lasts three to seven months. Typically you'll get shots one to three times a week. During the buildup phase, the allergen dose is gradually increased with each shot. This helps get your immune system more and more sensitized to the allergens that affect you.
• The maintenance phase generally lasts three to five years or longer. After your dose has been increased to an effective level during the buildup phase, you'll need a maintenance dose — which contains a consistent amount of allergens — about once a month.

In some cases the buildup phase is accelerated, which requires the injection of several injections of increasing doses during each doctor visit. This can decrease the amount of time you need to reach the maintenance phase and get relief from allergy symptoms, but it also increases your risk of having an adverse reaction.

Allergy shots are commonly used to control symptoms triggered by:

• Seasonal allergies. If you have seasonal allergic asthma or hay fever symptoms, you may be allergic to pollens released by trees, grasses or weeds.
• Indoor allergens. If you have year-round symptoms, you may be sensitive to indoor allergens such as dust mites, cockroaches, mold or dander from pets such as cats or dogs.
• Insect stings. Allergic reactions to insect stings can be triggered by bees, wasps, hornets or yellow jackets.

Allergy shots may be a good treatment choice if:

• It's impossible to avoid the things that cause your allergic reactions — and allergy medications aren't enough to control your symptoms
• Allergy medications cause intolerable side effects or interactions with other medications you need to take
• You want to reduce your long-term use of allergy medication
• You're allergic to insect stings

Allergy shots may not be a good choice if you have severe uncontrolled asthma, certain heart or lung problems, or if you take a beta blocker for heart problems.

If you're pregnant, starting treatment with allergy shots is usually not recommended. But if you're already getting allergy shots when you become pregnant, you can continue your treatment.

Allergy shots don't work for people with food allergies or chronic hives (urticaria).

Yes. Before starting allergy shots, your doctor may use a skin test to confirm that your reactions are caused by an allergy and determine which specific allergens cause your signs and symptoms. During a skin test, a small amount of the suspected allergen is scratched into your skin and the area is then observed for about 20 minutes. Swelling and redness indicate an allergy to the substance.

Your doctor may also use a blood test, such as the radioallergosorbent test (RAST) or the ImmunoCap test.

Allergy symptoms won't stop overnight. They usually improve during the first year of treatment, but the most noticeable improvement often happens during the second year. By the third year, most people are desensitized to the allergens contained in the shots — and no longer have allergic reactions to those substances. Most people need allergy shots for a few years. After that, some people remain desensitized after treatment stops. Others need to continue regular allergy shots to keep symptoms from returning.

If your symptoms don't improve after one year of regular allergy shots, your doctor will evaluate the situation. Perhaps the allergen dose needs to be adjusted or additional allergens must be added to the shots. Sometimes, allergy shots may be stopped in favor of other treatments.

It varies. For some people, treatment leads to a life without allergy symptoms, especially for children and people who undergo longer periods of treatment. Other people need to continue getting shots on a long-term basis to keep allergy symptoms at bay.

Allergy shots are generally safe. But they contain the substances that cause your allergies — so reactions are possible. These reactions could include:

• Local reactions. You may notice redness, swelling or irritation at the site of the injection. These normal reactions typically clear up within four to eight hours.
• Systemic reactions. These widespread reactions are less common — but potentially more serious. You may notice sneezing, nasal congestion and hives. More-severe reactions may include throat swelling, wheezing or chest tightness.
• Anaphylaxis. In rare cases, allergy shots can trigger a severe allergic reaction called anaphylaxis that causes low blood pressure and trouble breathing. An anaphylactic reaction can be life-threatening. If you get weekly or monthly shots on a regular schedule without missing doses, you're less likely to have a serious reaction.

The possibility of a severe reaction is scary — but you won't be on your own. You'll be observed in the doctor's office for up to 30 minutes after each shot, when the most serious reactions are likely to occur. If you have a reaction after you leave, return to your doctor's office or go to the nearest emergency room.

For children with allergies, allergy shots may prevent allergy-related asthma later in life. Allergy shots may keep kids from developing new allergies as well. Allergy shots can begin as early as age 5.

If you wonder whether allergy shots are right for you — or your child — there's plenty to consider. Ask yourself these questions:

• How severe are your symptoms? Allergy shots might be worth considering if your symptoms are severe or tough to manage. If you have seasonal allergies, the length of the season that gives you the most trouble might influence your decision.
• Are you happy with your current allergy medication? Shots are uncomfortable — or even frightening, especially for kids. But shots might be appealing if your allergy medication isn't working as well as you'd like or if you're struggling with significant side effects.
• Can you avoid your allergens? If the allergens that trigger your symptoms are unavoidable, allergy shots might offer an alternative to medication.
• Are you prepared for long-term treatment? Allergy shots require frequent clinic visits for at least several years.
• Is cost a concern? Find out whether allergy shots are covered by your health insurance plan.

Work with your doctor to better understand the pros and cons of allergy shots. Together, you can develop the best allergy management plan for you.

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