Before beginning drug desensitization, a physician will first determine what drug may be causing the allergic reaction. A series of allergy tests will be performed to ensure that the suspected drug is in fact responsible for allergy symptoms. These tests include:

• Allergy skin tests. A small amount of an allergen is introduced to the patient’s skin to determine if the person is allergic to that allergen. The development of redness or swelling in the test area usually indicates that the patient is allergic to the substance.
  

  

• Allergy blood tests. A sample of the patent’s blood is tested for antibodies (substances that indicate an allergic reaction has occurred) to a specific allergen.

Drug desensitization therapy takes place in a hospital or clinical setting for the patient's safety. The patient may be required to spend one day in the hospital, except in the case of aspirin desensitization, which may occur in a physician’s office. Patients should ensure that they have a ride home and expect that they may not feel well for a short time after therapy.

Desensitization for other allergies (e.g., pollen, dust, insect venom or pet dander) usually takes place over months. Drug desensitization therapy, however, typically takes place over hours or days. This decreased time frame may be referred to as rapid protocol desensitization. The type of medication influences the length of time for desensitization. For instance, desensitization for antibiotic allergies typically takes place over a matter of hours. Other desensitization protocols (e.g., aspirin allergies) take longer, occurring over a number of days.

The patient is introduced to small but increasing amounts to the drug either through oral ingestion or injections. The method of drug desensitization is determined by the type of drug, allergic symptoms and other factors. Desensitization may be more effective for some medications when administered through a particular method.

After the first dose is introduced, patients will be asked to wait for a specific time period until the next dose. The patient remains at the facility during the entire desensitization therapy procedure and will be monitored for some time after each dose to ensure that a significant allergic reaction is not occurring. Should allergy symptoms appear during the desensitization therapy, allergy medications should be administered to relieve the symptoms. These commonly include antihistamines, corticosteroids or epinephrine (in the case of anaphylactic shock). Most allergic reactions occurring during drug desensitization therapy can be managed with these allergy drugs without interrupting the desensitization process.

The time between doses will vary from a few minutes or hours, to a few days. Also, the time between doses may increase after each dose until the patient reaches the “maintenance” phase of immunotherapy.

For some medications, such as aspirin, patients will still need periodic doses of the drug to maintain their tolerance to the substance after desensitization is achieved. How long it takes until maintenance is achieved depends on the medication. For instance, antibiotic desensitization is rarely followed by a maintenance stage, because the need for these medications is usually immediate and short-term.