What is allergen immunotherapy?
Allergy immunotherapy involves exposing a person to various allergens over the course of years to sensitize them to the substance, reducing the autoimmune reaction that causes allergic symptoms. Ideally, immune therapy reduces dependence on allergy medication.
Some people tend to develop severe allergic reactions to common substances which normally do not provoke an immune reaction in most people. Immunotherapy is a long-term treatment and gradually makes a person’s immune system more tolerant to the allergens.
Allergen immunotherapy is of two types:
- Subcutaneous: Injections given in the tissue beneath the skin, usually in the upper arm.
- Sublingual: Tablets which the patient keeps under the tongue for a couple of minutes before swallowing. Sublingual drops may also be also used, but are not approved by FDA.
Why do allergies occur?
Allergies occur when a person’s immune system overreacts to minor toxins or harmless substances present in the environment such as:
- Dust mites
- Animal dander
- Stinging insects
Exposure to allergens causes certain immune cells known as mast cells to release inflammatory compounds such as histamine, which causes the allergy inflammation symptoms. The mast cells also release cytokines that activate other immune cells which contribute to the worsening of symptoms.
What are the allergic diseases treated with immunotherapy?
Immunotherapy is a useful treatment option for people who are unable to avoid exposure to allergens. Allergen immunotherapy can be used to treat allergic conditions such as:
- Seasonal allergic rhinitis
- Perennial rhinitis
- Allergic asthma
- Eye allergies such as conjunctivitis
- Insect venom anaphylaxis
- Atopic dermatitis
Immunotherapy may not be suitable for
- People with uncontrolled or severe asthma
- People with heart or lung disease
- Children younger than five years of age
- Pregnant women, though therapy may be continued if a person got pregnant while on immunotherapy
How is allergen immunotherapy administered?
An allergist or immunologist schedules the immunotherapy treatment for an allergy patient. Before starting immunotherapy, the immunologist typically takes the following steps:
- Records a complete history of the patient’s allergic symptoms.
- Checks existing medical conditions and medications.
- Performs a skin prick test that places a small amount of an antigen in the skin to find substances to which the patient is allergic.
- Prepares a diluted solution of specific antigens that cause the patient’s allergic symptoms.
Subcutaneous immunotherapy is performed in two phases:
- Buildup phase: Once- or twice-weekly injections for six months to a year, starting with a low dose, gradually increasing until the patient is able to tolerate the maintenance dose. The maintenance dose is calibrated to roughly equal the levels of allergens present in the patient’s environment.
- Rush immunotherapy: The buildup phase may be speeded up by a higher dose increase every week for patients who can tolerate it. Though it reduces time required to reach maintenance dose, it also increases the risks of a severe allergic reaction.
- Maintenance phase: The maintenance dose of injections are usually given once every two or three weeks for three to five years, depending on the patient’s response to the therapy.
- The patient remains under observation for about 30 minutes after each allergy shot to check for any severe allergic reactions.
Sublingual immunotherapy is the use of common seasonal allergy-causing antigens in tablet form, usually for patients who are unable to take regular injections for any reason. The patient holds the tablet under their tongue for up to two minutes before swallowing it.
Sublingual immunotherapy tablets are typically taken once daily starting approximately four months before the allergy season and continued through the season. The sublingual immunotherapy is started in the allergist’s office so that the patient can be monitored for a possible severe allergic reaction.
Following are the FDA-approved sublingual tablets:
- Oralair: Calibrated pollen extract of five types of grasses, approved for patients from age five to 65.
- Grastek: Approved for patients from age five to 65 for Timothy grass allergy.
- Ragwitek: Approved for patients 18 years or older for ragweed allergy.
- Odactra: Approved for patients 18 years or older for house dust mite allergy.
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Does immunotherapy work for allergies?
Allergy shots reduce the activity of the inflammatory immune cells and bring down the sensitivity to allergens. If allergen immunotherapy is faithfully followed for the required duration, there is a good chance of improvement or even complete remission from allergy symptoms.
Symptoms usually start gradually abating in the first year, and by the third to fifth year, many people may find complete relief and be able to stop taking the shots. About 85% of people with hay fever report improvement from allergen immunotherapy.
What are the risks and side effects of allergen immunotherapy?
A major downside to allergen immunotherapy is the time commitment it requires. Side effects are usually mild and resolve on their own in most people. Rarely, some patients may have anaphylaxis, which is a serious reaction to the injection which can cause symptoms such as:
Side effects of subcutaneous immunotherapy include:
- Injection site reactions such as:
- Systemic reactions such as:
- Serious side effects include:
Side effects of sublingual immunotherapy include: