Immunotherapy for allergic diseases (2)

So how do we treat allergies?  The most obvious answer is to avoid coming in contact with allergens.  To successfully practice allergen avoidance, we must first find out what the person is allergic to, and to confirm that these allergens are responsible for their symptoms.  A positive skin test will identify allergens that the patient responds to immunologically, but it still does not confirm that these allergens cause symptoms from day to day.  A careful history will be very helpful, but sometimes, challenge studies might be needed.  Measuring the level of allergens in the patient’s living and working environment might also be useful.  For certain indoor allergens such as house dust mites and animal dander, avoidance measures can be extremely helpful.  The second line of treatment for allergies is drug treatment.  Drugs such as antihistamines are used to counteract some of the symptoms of an allergic reaction.  They can be useful for mild cases but are frequently not successful in controlling more severe cases.  Steroid spray is also very useful in reducing the inflammation caused by an allergic reaction.  These treatments do not address the root of the problem, and symptoms promptly recur once the patient stops the treatments.

The only method to eliminate allergies is by immunotherapy.  This form of therapy aims to induce immunological tolerance to specific allergens, so that patients will no longer react to them when exposed.  Traditionally, immunotherapy (also called allergy injections or desensitization) is administered by repeated subcutaneous injections of purified allergen extracts.  This carries a risk of severe allergic reactions, and the injections must be administer under the supervision of an experienced allergist with adequate emergency support.  In experienced hands, immunotherapy is very safe, especially if standardized extracts are used.  In patients with insect sting allergy, immunotherapy is >99% effective in protecting the patients from future stings, and the effect appears to be lifelong after 3 to 5 years of continuous treatment.  The effectiveness of pollen immunotherapy has also been shown to last for at least 3 years after stopping treatment.

 

Newer forms of immunotherapy are being developed.  Sublingual immunotherapy uses a very high dose of allergen extract to be placed under the tongue for absorption.  Initial studies suggest that it might be effective for allergic rhinitis and possibly asthma.  More studies are needed to confirm its efficacy and also to determine its mechanism of action.  We are currently conducting a large clinical study, which will eventually involve 120 patients with allergic rhinitis, to evaluate sublingual immunotherapy against house dust mites.  Patients with moderate to severe allergic rhinitis will be recruited.  Skin tests to common allergens will be performed to confirm sensitization to house dust mites.  A nasal challenge study will be performed to confirm that house dust mites can indeed cause nasal symptoms.  The patients will first be given conventional drug therapy including an antihistamine and a nasal spray.  Patients who do not derive satisfactory results from this treatment will be randomized to receive immunotherapy or placebo for one year.  The patients will be reevaluated every three months, and those that respond to treatment will have their nasal spray gradually withdrawn.  Patients will fill in a report of their symptoms every week.  At the end of one year, all patients on active treatment will continue for another year, and those on placebo will be switched to active treatment.  Immunological parameters in the blood and nasal washings will be evaluated at the beginning of the study and after one year.]

 

 

 

Reference information: hkucc.hku.hk

The information aims to provide educational purpose only. Anyone reading it should consult physician before considering treatment and should not rely on the information above.