Immunotherapy for allergic diseases (III)

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.

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.

參考資料: www.allergy.hk

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