Allergy Shots – Conditions, Risk & Alternatives

Allergy Shots

Also called: Enzyme Potentiated Desensitization, Low Dose Immunotherapy, Rush Immunotherapy, EPD, Accelerated Immunotherapy, Desensitization

Reviewed By:
Marc J. Sicklick, M.D., FAAAAI, FACAAI


Allergy shots are a form of allergy and asthma treatment in which increasing, controlled doses of an allergen are injected into a patient over a period of time. The goal is to increase the patient’s tolerance to the allergen while reducing symptoms brought on by an allergic reaction.  

Allergy shots are used to treat allergic rhinitis (hay fever) symptoms, such as sneezing, watery eyes and runny nose; and symptoms associated with insect stingallergies. Breathing problems associated with asthma can be triggered by certain allergens. Therefore allergy shots can also help prevent asthma attacks in some people with asthma.

Allergy treatment more commonly involves a mixture of avoidance (completely avoiding the allergen) and one or more allergy medications to prevent or relieve symptoms. Allergy shots may be recommended when other treatments fail or in severe cases. Shots may be recommended to a person who has a life-threatening reaction to insect stings, for instance.

The goal of allergy shots is to increase the body’s tolerance to a certain allergen, to accomplish one or more of the following:

  • Prevent the onset of symptoms
  • Lessen the frequency of reactions
  • Lessen the severity of symptoms resulting from a reaction

Allergy shots are not effective for everyone, and there are risks to the treatment that must be weighed. However, many who suffer from allergies or asthma find long-lasting relief as a result of immunotherapy.

About allergy shots

Allergy shots (immunotherapy) are a treatment in which an offending allergen is injected under a patient’s skin in tiny doses. Common allergens include pollens, pet dander, dust, or the venom contained in certain insect stings (such as bees, wasps, hornets, fire ants). In some cases, a physician will use allergy shots to desensitize an individual to certain drug allergies. This may be done when the drug is vital to the patient’s health and when there are no alternatives. However, most physicians prefer instead to look for alternative drugs to replace the drug to which the individual is allergic.

The goal of allergy shots is to increase the body’s tolerance of a specific allergen. In many cases, the patient’s tolerance level to these allergens rises dramatically, causing a significant reduction in symptoms such as runny nose, itchy eyes and scratchy throat. This accomplishes one or more of the following:

  • Prevents the onset of symptoms
  • Lessens the frequency of reactions
  • Lessens the severity of symptoms resulting from a reaction

Those who undergo allergy shot treatment report high success rates, especially in the treatment of allergic rhinitis. According to a study published in the Annals of Allergy, Asthma & Immunology:

  • 81 percent of patients felt the therapy had been a success
  • 19 percent were unsure of the shots’ effectiveness
  • Emergency room visits declined by 68 percent
  • Days lost from school dropped by 75 percent

It is not clear how allergy shots build this tolerance. In some cases, researchers have found that the injections stimulate the production of blocking immunoglobulin G (IgG) antibodies, which bind to the allergen. This is important, because it prevents another antibody – immunoglobulin E (IgE) – from binding to the allergen. IgE is the antibody that triggers mast cells to start the allergic reaction. The shots may also decrease the body’s production of IgE.

Potential immunotherapy candidates undergo extensive allergy skin tests, blood tests and physical examination to help pinpoint the offending allergen. During the first injection, the patient will receive a saline solution (dilute salt water) mixed with a very low dose of the troublesome allergen. The patient typically is monitored for 30 minutes to make sure the injection has not triggered a reaction such as shortness of breath, runny nose or tight throat. In addition, patients will be monitored for signs of anaphylaxis, a rare, life-threatening allergic reaction that demands immediate medical attention.

Patients who do not have a reaction to the trace amount of allergen usually will be discharged until the next treatment session. If patients have a reaction after leaving the medical facility, they should immediately return to the facility or visit an emergency room.

After the initial injection, a patient will return for periodic follow-up treatments. These injections typically take place once or twice a week over the course of several years. With each successive treatment, the amount of allergen injected under the skin is increased.

When effective, immunotherapy can dramatically reduce a patient’s sensitivity to certain allergens, with the first benefits becoming apparent in as little as six months.

Once the first phase of treatment is finished, injections are given with less frequency, typically monthly for a period of three to seven years. At some point, the patient’s tolerance may grow to the point where further shots are unnecessary. Generally, discontinuation of the treatments is recommended after a patient has demonstrated minimal symptoms over two consecutive seasons of exposure. Those who begin to experience symptoms again later can undergo another round of immunotherapy.

Though allergy shots are currently available only as an injectable treatment, a similar method of immunotherapy that involves medicine placed under the tongue has proven effective in early testing. Though more research is required before the treatment is accepted by the wider scientific community, this type of immunotherapy may one day be available as an alternative to allergy shots.

Conditions treated with allergy shots

Not all patients with allergies or asthma are candidates for allergy shots. The process is time consuming and not effective for everyone. Physicians generally will try other forms of treatment – such as medications or lifestyle modification measures designed to reduce exposure to allergens – before recommending immunotherapy. A physician may recommend allergy shots if patients:

  • Have been unsuccessful with other forms of therapy such as lifestyle changes or allergy medications.

  • Are unable to tolerate the side effects of allergy medications.

  • Suffer with symptoms related to their allergy for all or most of the year.

  • Find that they cannot avoid the allergen in their daily lives.

  • React to airborne allergens, including pollens, dust, molds and animal dander.

  • Experience multiple complications from their allergies, including headache, asthma, allergic conjunctivitis and sinus or ear infections.

  • Are allergic to insect stings. Many individuals have life-threatening reactions to insect stings, making immunotherapy a vital option.

Allergy shots may also be used to treat cases of allergic asthma in children. This can result in a reduction of symptoms and less need for allergy medications in those whose allergies trigger asthma symptoms.

In some cases, when a patient with a drug allergy urgently requires that specific drug, desensitization may be attempted. However, the process can be dangerous, and a physician usually will prefer using an alternate drug.

Allergies that do NOT respond well to immunotherapy include those related to the following allergens:

  • Foods or food additives
  • Feathers and kapok (mattress filling)

In addition, hives and eczema do not respond well to allergy shots. Therefore, people whose allergies primarily cause skin rash symptoms may not be candidates for allergy shots. However, hives or eczema that is associated with allergic rhinitis or asthma may disappear after allergy shots have been given for those conditions.

The vast majority of patients whose conditions warrant immunotherapy respond favorably to the treatment. In some cases, patients may still be largely symptom-free years after their last allergy shot.

For a smaller percentage of patients, allergy shots are not effective in treating their condition. Individuals who have allergies to many different allergens are less likely to benefit from immunotherapy.

Conditions of concern with allergy shots

By and large, immunotherapy is a safe way to treat many allergies and some cases of asthma. However, individuals with certain conditions or diseases may face health risks that make immunotherapy a poor treatment option. These include people with one or more of the following factors:

  • Impaired immune systems. Those with autoimmune diseases, such as lupus (a chronic skin disease) or AIDS, should not undergo immunotherapy. Allergy shots in these patients can spur the creation of immunoglobulin g (IgG) antibodies, leading to the creation of antigen-antibody complexes. This process can bring about immune-related conditions.

  • Heart disease (including high blood pressure). Patients with some heart conditions are not candidates for allergy-shot treatments. Those undergoing immunotherapy face a small risk of experiencing the life-threatening allergic reaction known as anaphylaxis, which is more likely to be fatal for those with heart conditions. 

  • Beta-blocker use. Those who take beta blockers to treat high blood pressure or a heart condition may not be good candidates for immunotherapy. Beta blockers can counteract the effects of epinephrine, the only drug that effectively reverses the symptoms of anaphylaxis, a rare but life-threatening allergic reaction that can be triggered by testing.

  • Monoamine oxidase inhibitor use. These antidepressants also counteract the effects of epinephrine, which is used to reverse the symptoms of anaphylaxis.

  • Pregnancy. Pregnant women and those considering becoming pregnant should tell their physician before beginning a course of immunotherapy. Pregnancy does not preclude immunotherapy treatments, though it may be necessary for women to take steady allergy shot doses during the pregnancy (without increasing the dosage).

  • Uncontrolled asthma. Many individuals with asthma can benefit from allergy shots, but asthmatics have a higher risk of experiencing anaphylaxis while undergoing immunotherapy. Those with asthma should not engage in immunotherapy unless their condition is under control.

Age may also play a role in the effectiveness of allergy shots. Immunotherapy is less likely to be effective in patients over 55. However, it still reduces the symptoms of many older patients. In very young children (under 5), allergy shots may not be advised. However, research has emerged that giving allergy shots to children under 5 may help slow or stop the development of allergies later in life. Research is continuing, and parents should discuss any questions regarding allergy shots with their physician.

Immunotherapy involves regular injections over a long period of time. Parents and healthcare providers must be sensitive to the fears that even older children have about needles. When allergy shots are recommended, fully explaining the immunotherapy process and talking with a child about his or her concerns can help alleviate their fears.

Before, during and after allergy shots

Patients who have been approved to undergo immunotherapy will first need to pinpoint the allergen to which they react. This is usually accomplished through an allergy skin test, in which small amounts of one or more allergens are introduced to the skin, and through blood tests.

Once an allergen has been identified, the first allergy shot is scheduled. An individual preparing to undergo immunotherapy may be advised to take the following precautions:

  • Avoid exercise for two hours before an appointment

  • Inform physician of all current medications, especially beta blockers (used in the treatment of heart-related problems or high blood pressure) or monoamine oxidase inhibitors (used in the treatment of depression)

  • Tell physician about pregnancy or plans to become pregnant

Because patients risk severe reactions after receiving an allergy shot, the treatment should be administered only under the supervision of a physician who is trained in immunotherapy and prepared to treat potentially life-threatening emergencies.

During the first session, a solution of diluted salt water (saline) is combined with a very small dose of the allergen. This is injected under the patient’s skin, usually in the back of the upper arm. Patients who fear needles can be reassured that allergy shots are much less painful than the deep, intramuscular injections given during standard immunizations. The needles used in allergy shots are very fine-tipped, and they are injected just below the skin’s surface rather than into the muscle.

After the first injection, the physician monitors the patient for about 30 minutes to make sure no allergic reaction or other symptoms occur. In very rare instances, a whole-body allergic reaction known as anaphylaxis can occur. Left untreated, anaphylaxis can quickly progress to life-threatening anaphylactic shock, which is characterized by difficulty breathing and a dangerous drop in blood pressure. If this rare reaction occurs, the physician may administer a dose of epinephrine, corticosteroids and intravenous (I.V.) fluids, which usually reverses symptoms rapidly.

Those who suffer from asthma should also be sure to carry their rescue medication (e.g., bronchodilator) with them in case respiratory symptoms develop following an injection.

Patients may experience other, far less dangerous, symptoms during an immunotherapy session. These include:

  • Redness or flushing
  • Warmth of skin or hot flashes
  • Mild itching
  • Slight swelling at the shot site

Such mild symptoms usually disappear within four to eight hours. A physician may recommend cold compresses, oral antihistamines or topical corticosteroids to relieve these symptoms.

Patients who do not have a reaction to the trace amount of allergen are likely to be discharged until the next treatment session. Though anaphylaxis often begins immediately after an individual has been exposed to a particular allergen, it can sometimes occur several hours after exposure. If patients have a reaction after leaving the medical facility, they should immediately return to the facility or visit an emergency room. Many allergists also prescribe an allergy kit in case a reaction occurs after leaving the medical facility.

After the initial injection, a patient will return for periodic follow-up treatments. Though the frequency of follow-up injections varies depending on the physician, these injections typically take place once or twice a week over the course of several years. With each successive treatment, the amount of allergen injected under the skin is increased, and the body gradually is desensitized to the allergen.

Patients who experience an anaphylactic reaction after receiving an allergy shot typically continue treatment. However, the subsequent injection will contain a reduced dosage of the allergen. This helps the patient’s body build up its immunity more gradually.

After about six months, some physicians reduce the injection frequency to once a month (known as a “maintenance dose”) for three to five years. At this point, some patients no longer need shots and are symptom-free for years. If symptoms return, the injections begin again.

It is important for patients receiving allergy shots to keep all of their immunotherapy appointments. The treatment method is successful only when the shots are given on a predetermined schedule.

Immunotherapy patients generally do not notice great improvement right away. It can take up to a year before they notice any significant change in symptoms.  During the second year, substantial improvements should be evident. When an improvement is not seen after a year of maintenance therapy, physicians will look for possible factors interfering with the treatment. These may include inadequate doses of the allergen or failure to identify allergens during initial allergy testing. When such a factor cannot be found, physicians may choose to discontinue immunotherapy and pursue alternative treatment options.

Potential risks with allergy shots

Anaphylaxis (a severe allergic reaction affecting two or more body systems) is the most serious potential side effect of allergy shots.  The condition can quickly progress to life-threatening anaphylactic shock, which is characterized by difficulty breathing and a dangerous drop in blood pressure. Symptoms of anaphylaxis include:

  • Hives on areas of the body other than the injection area

  • Shortness of breath

  • Chest pain or tightness

  • Swelling of the throat or tongue (angioedema)
  • Choking

  • Loss of consciousness

A medical professional can administer epinephrine (and, possibly, an antihistamine), which usually provides immediate relief from the dangerous reaction. Those with medical conditions such as asthma are at increased risk for anaphylaxis, so the condition must be well-controlled before any asthmatic undertakes immunotherapy. Though rare, the risk of anaphylaxis must be weighed by anyone considering immunotherapy.

More common – and less serious – potential side effects include:

  • The triggering of allergic rhinitis or asthma symptoms

  • Itching or hives

  • Swelling of the skin near the injection site or of the entire arm

  • Burning, stinging or redness at the injection site

These symptoms usually pass within a few hours.

Alternatives and variations with allergy shots

Though standard immunotherapy involves injections over a period of months, weeks and years, there also are other forms of the treatment, including:

  • Accelerated immunotherapy. Sometimes called “rush” immunotherapy, this consists of a series of allergy shots given every few hours during the course of a single day. The healthcare professional in charge of the therapy watches closely to see whether a reaction occurs to the first shot. If not, the therapy continues.

    The advantage of accelerated immunotherapy is that the patient graduates to the maintenance stage of treatment over the course of about five to eight days, as opposed to the several months necessary for those undergoing standard immunotherapy. The “rush” approach is most likely to be used for those with:

    • Life-threatening allergic reactions to insect stings

    • Homes a long distance from any health care facility

    • Severe allergic asthma

    • Plans to travel for extended periods of time

  • Oral immunotherapy. In this treatment, drops placed under the tongue replace injections in the arm. The patient swallows the drops, which can be administered at home. Although this treatment is used in Europe, the U.S. Food and Drug Administration (FDA) has yet to approve any oral extract for use in immunotherapy treatments in the United States.

  • Enzyme potentiated desensitization (EPD). Also called “low-dose” immunotherapy, this involves a combination of a very low dose of an allergen and an enzyme called b-glucuronidase. Despite several clinical studies, EPD has not been proven to be an effective therapy. For this reason, mainstream allergists do not recommend its use. Proponents say the advantage of EPD is that it treats symptoms related to a broad range of allergens, including those related to food allergies. In addition, EPD does not require weekly shots. Patients who receive a recommendation of EPD from their physician should seek a second opinion from a board-certified physician. 

Questions for your doctor

Preparing questions in advance can help patients to have more meaningful discussions with their physicians. Patients may wish to ask their doctors the following questions related to allergy shots:

  1. Am I a candidate for allergy shots?
  2. What risks do I face by undergoing immunotherapy?
  3. What will happen if I experience anaphylaxis after receiving an allergy shot?
  4. Will I experience pain while receiving the allergy shots?
  5. What are the odds that the treatment will fail to relieve my condition?
  6. How often will I need to receive allergy shots? How long will the treatment continue?
  7. Will the desensitization I experience from allergy shots be permanent?
  8. Are there any precautions I should take before undergoing immunotherapy?
  9. What will happen if I begin to experience symptoms again after a long period of being symptom-free?
  10. Will I have to cease treatment if I become pregnant?
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