The answer to this question can be simply stated as: patient’s preference. There are certainly some guidelines for the administration of immuntherapy that usually consider a good candidate for immunotherapy, the patient that does not respond well to medication management. The guidelines also advise not to give immunotherap to children younger than 5 years or very sick patients.
Some common sense and patient preferences need to be considered when indicating immunotherapy. In general the patient that will seek immunotherapy is the one that has persistent symptoms that affect his/her quality of life, symptoms that persist for a long period of time, and/or that do not respond well to medication. Also patients with severe conditions like asthma, are a special group, as immunotherapy is the only treatment available with the potential to revert asthma to a normal lung function. Patients with conditions like Migraine are also a special group as Migraines are often of allergic orogin, and often do not respond well to usual therapy but do respond well to immunotherapy.
The important concept about immunotherapy is that it is the only treatment available that can revert the immunological reactivity of the individual from a dysfunctional system (implying production of IgE and the potential to elicit reactions) to a non-dysfunctional system -producing IgG that lacks the potential for elicitation of symptoms. In other words: Immunotherapy is the only treatment available that can cure a patient improving the symptoms to a significant degree and producing a long lasting effect sustained long after the discontinuation of immunotherapy.
The main problem with immunotherapy is that it is a long treatment. An average treatment lasts around 5 years. An important remark is that a well implemented course of immunotherapy does not take 5 years to make the patient better. On the contrary patient will feel better in a period of months. The reason for the long treatment time is to accomplish a long term relief of the symptoms. In the great majority of the patients treatment with a strong dose of immunotherapy for 5 years will produce a life-long lasting protective effect.