If antihistamines and nasal sprays are not effective or not tolerated by the patient, other types of therapy are available. Allergy desensitization or immunotherapy may be needed. Allergy immunotherapy stimulates the immune system with gradually increasing doses of the substances to which a person is allergic. Because the patient is being exposed to the allergy-inducing substance, an allergic reaction can occur and this treatment should be supervised by a physician. Although the exact way allergy desensitization works is not completely known, allergy injections appear to modify or stop the allergic reaction by reducing the strength of the IgE and its effect on the mast cells. This form of treatment is very effective for allergies to pollen, mites, cats, and especially stinging insects (for example, bees). Allergy immunotherapy usually requires a series of injections ( allergy shots ) and takes three months to one year to become effective. The required length of treatment may vary, but three to five years is a typical course. Frequent office visits are necessary.
Serum levels are normally less than ng/mL.  Elevated levels of serum tryptase occur in both anaphylactic and anaphylactoid reactions, but a negative test does not exclude anaphylaxis . Tryptase is less likely to be elevated in food allergy reactions as opposed to other causes of anaphylaxis. Serum typtase levels are also elevated in and used as one indication suggesting the presence of eosinophilic leukemias due to genetic mutations resulting in the formation of FIP1L1-PDGFRA fusion genes or the presence of systemic mastocytosis .