Allergen immunotherapy, also known as allergy shots, is often used to treat patients who suffer from severe allergies or who experience allergy symptoms more than three months a year. Allergen immunotherapy involves injecting increasing amounts of a diluted allergen into a patient over several months.
Rather than treating the symptoms of allergies, immunotherapy treats the immune system, which is responsible for an allergic reaction. An allergic reaction occurs when the body is exposed to an antigen (foreign substance like pollen, dust mites, mold and pet dander) that is mistakenly identified as a harmful invader. The white blood cells produce an antibody (immunoglobulin E) to the antigen. This process is called sensitization.
Once the body is sensitized, the immune cells will release chemical mediators like histamine when the antigen enters the body. These mediators cause inflammation, as well as allergy symptoms, such as sneezing, runny nose, watery eyes and hives.
Allergy shots desensitize the patient's immune system so it will not react to the antigen. After therapy, the white blood cells produce less immunoglobulin E when the antigen enters the body. The lower amounts of immunoglobulin E mean that a patient's body is not as sensitive to the antigen and allergy symptoms are reduced.
According to the American Academy of Allergy Asthma & Immunology, immunotherapy is only recommended for patients who have allergic asthma, allergic rhinitis (hay fever, an allergic reaction that causes inflammation of the nose), conjunctivitis (pinkeye) and stinging insect allergies. Immunotherapy is not recommended for patients who have food allergies. There is conflicting scientific evidence of the use of immunotherapy for the treatment of atopic dermatitis.
Immunotherapy does not cure allergies, but it may help reduce the body's sensitivity to certain substances. During therapy, some patients may not experience any allergy symptoms. Immunotherapy has shown to prevent the development of new allergies and, in children, it can prevent the progression of allergic rhinitis to asthma. However, the effectiveness of immunotherapy depends on how severe the patient's allergies are, as well as how many substances the patient is allergic to.
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Before receiving immunotherapy, patients should tell their healthcare providers if they are taking any drugs (prescription or over-the-counter), herb or supplements.
Patients should not engage in any vigorous physical activity two hours before and after treatment. Exercise may increase the blood flow to the tissues and promote faster release of antigens from the allergy shot into the bloodstream.
Patients should consult their healthcare providers about the safety of immunotherapy if they are pregnant or trying to become pregnant. If a pregnant woman experiences anaphylaxis in response to immunotherapy, the fetus may be harmed.
how it is performed
Allergen immunotherapy works like a vaccine. A diluted extract of the allergen that the patient is allergic to is injected into the patient. The patient responds to the treatment by developing an immunity or tolerance to the allergen. As a result of these immune changes, immunotherapy can lead to decreased, minimal or no allergy symptoms when the patient is exposed to the particular allergen again.
There are two phases of immunotherapy -
the build-up phase and the maintenance phase. During the build-up phase, allergy shots are injected into the upper arm once or twice a week for several months (typically three to six months). The dose is gradually increased until the maintenance dose is reached.
The maintenance phase begins once the effective therapeutic dose is reached. This dose is different for each patient because it depends on the patient's level of allergen sensitivity and their response to immunotherapy during the build-up phase. Once the maintenance dose is reached, the patient will continue therapy every two to four weeks for two to five years or more.
There are two types of side effects associated with immunotherapy -
local and systemic (occurring in many areas throughout the body).
Local reactions are relatively common and may include redness and swelling at the injection site. This can occur immediately after treatment or several hours later.
Systemic reactions are much less common, and they are usually mild and responsive to medications. Symptoms typically develop within 30 minutes of treatment and require immediate treatment. Symptoms may include increased allergy symptoms like nasal congestion, hives or sneezing. A rare, but life-threatening reaction called anaphylaxis has also been reported. Symptoms of anaphylaxis can vary from mild to severe The most dangerous symptoms are low blood pressure, breathing difficulties, shock and loss of consciousness, all of which can be fatal. Anaphylaxis is an emergency condition that requires immediate medical attention. Epinephrine is a medication used to treat severe allergic reactions such as anaphylaxis. Administering the epinephrine as soon as possible improves the patient's chance of survival and a quick recovery.