Allergic Rhinitis (Hay Fever and Rose Fever) and Chronic Nasal Congestion

Description

Alternative Names

Immunotherapy

Immunotherapy (commonly referred to as "allergy shots") is a highly effective treatment for patients with allergies. It is based on the premise that people who receive injections of a specific allergen will lose sensitivity to it. The most common allergens for which shots are given are house dust, cat dander, grass pollen, and mold.

Immunotherapy has many advantages:

• It targets the specific allergen.
• It may reduce sensitivity in airways in the lungs as well as in the upper airways.
• It may help prevent the development of new allergies in children.
• It is proving to reduce asthma symptoms and the use of asthma medications in patients with known allergies.

Candidates

Candidates for Immunotherapy. Immunotherapy (allergy shots) may be given to anyone over seven whose allergies are severe and do not respond to medication. At an international 2000 conference, many experts agreed that immunotherapy should be considered as soon as possible for children with asthma and allergies. Immunotherapy is safe for pregnant women who are already receiving it, although half-strength doses are generally recommended and it should not be started during pregnancy.

Individuals at Risk for Complications. People who should probably avoid immunotherapy include the following:

• People who have an extreme response to skin tests. This may predict an allergic reaction.
• People who are actively wheezing.
• Patients with uncontrolled severe asthma or lung disease.
• Patients taking certain medications (such as beta-blockers).
• The health status of anyone should be determined before starting treatment.

Administering Therapy

The major downside to immunotherapy is that it requires a prolonged course of weekly injections ("allergy shots"). The process generally follows this course:

• Injections of diluted extracts of the allergen are given on a regular schedule, usually twice a week to weekly at first, then in increasing doses until a maintenance dose has been reached. It usually takes several months and may take up to three years to reach a maintenance dose.
• At that time, intervals between shots can be two to four weeks, and the treatment is continued for up to three to five years.
• Patients can experience some relief within three to six months; if there is no benefit within 12 to 18 months, the shots should be discontinued.

After stopping immunotherapy, about one third of allergy sufferers no longer have any symptoms, one third have improved symptoms, and one third relapse completely.

The use of an injection series is effective but patients often fail to comply with the regimens. Some other schedules and delivery methods are being investigated that might make the program easier and less distressing.

Rush Immunotherapy. Investigators are studying so-called rush immunotherapy, in which patients achieve the full maintenance dose with several shots a day over a period of three to five days. Rush therapy uses modifications that reduce the risk of severe reactions to excessive doses. Studies are suggesting that it is effective and safe, with few side effects other than itching. Patients must be monitored closely during this period, however, for severe reactions.

Oral Forms. Trials are underway to test oral forms of immunotherapy. One method uses an oral gelcap and another uses a sublingual (under-the-tongue) tablet. In one study, the sublingual approach was safe but less effective than shots, but it still might be useful for mild conditions. (Previously, oral forms have not been feasible at all because digestive enzymes in the intestine rendered the therapy useless.)

Side Effects and Complications of Immunotherapy

Injections for ragweed and, possibly, excessive doses of dust mites, have higher risks for side effects than other allergy shots. If complications or allergic reactions develop, they usually occur within 20 minutes although some can develop up to two hours after the shot is given.

Side effects of immunotherapy include the following:

• General itching, swelling, red eyes, hives, soreness at the injection site.
• Rarely, low blood pressure, asthma exacerbation, or difficulty breathing. This is due to an extreme hypersensitivity response called anaphylaxis. It can also occur if excessive doses are given.
• In rare cases, particularly because of excessive doses or if a patient has a serious lung problem, severe reactions can occur, which can be life threatening.
• Premedicating patients with antihistamines and corticosteroids may help reduce the risk of reactions to immunotherapy, although this could mask early warning signs. This option should be used only after discussion with the doctor.

In one 10-year study, the incidence of any adverse effect was less than two-tenths of one percent, and the great majority of events were mild. The risk for a fatal response is estimated to be one per 63 million injections. (As a comparison, the risk for a fatal reaction to penicillin is much higher, one per 7.5 million injections.)

Investigative Immunotherapy Approaches

Vaccines. Of particular interest is the development of immunotherapeutic vaccines that use more specific targets to produce an insensitivity to allergens. One such vaccine uses a small protein from the allergen, which is injected into the patient. Other vaccines under investigation are those that use the allergen's genetic material (its DNA) to promote tolerance to the allergen.

Monoclonal Antibodies. Monoclonal antibodies (MAb) are genetically-developed antibodies that are designed to target and attack very specific factors. A MAb known as omalizumab (Xolair) prevents the antibody immunoglobulin E (IgE) from triggering the inflammatory events that lead to allergies. Studies in 2002 and 2003 suggested that omalizumab is very effective in significantly improving seasonal allergies and allergy-related asthma.