Desensitization therapy is a technique used to reduce a patient’s allergic reactions to allergy-provoking substances. This therapy can be used to help with substances individuals cannot avoid. People with diabetes may be prescribed this treatment to help overcome allergies to insulin, a medication that may be prescribed to control glucose (blood sugar).

An allergy occurs when the immune system identifies a generally harmless substance as being dangerous and produces antibodies to fight the substance. Any substance that causes this reaction is called an allergen.

In some cases, an allergic person can avoid contact with the allergen. However, when people become allergic to medications necessary for their health, such as insulin, avoidance may not be possible. Desensitization is the process of reducing or eliminating a patient’s sensitivity to an allergen. This is accomplished over time by injecting the patient with small but increasing amounts of the allergen. When this process is used to reduce allergic reactions to medications, it is called drug desensitization therapy.

Insulin allergies are rare. They usually appear in one of two forms:

• Local reaction. This reaction is limited to the injection site. Symptoms include red and itchy skin.
  
  
• Systemic reaction. This is a reaction that affects the entire body. Symptoms include hives, red patches across the body, galloping heartbeat and breathing difficulties.

Drug desensitization is considered only when there is no alternative type of insulin or other medication available. This process must be carefully supervised by a physician, sometimes in a hospital.

The patient continues to have allergic reactions to the drug while desensitization takes place. Antihistamines, corticosteroids, epinephrine or other medications may be given to suppress any allergic symptoms while the desensitization process is completed. 

Insulin desensitization is commonly performed using synthetic insulin with a rapid desensitization protocol, an increased time frame in which desensitization is achieved in a matter of hours or days.

Severe allergic reactions, including anaphylaxis (reactions involving two or more body systems), are sometimes possible during drug desensitization therapy. Desensitization may not be an option for patients at risk for such reactions. In such cases, patients will probably need to consult with their physician about alternative forms of therapy – for example, switching from animal insulin to human insulin, or taking drugs such as corticosteroids to reduce antibody activity. 

Drug desensitization therapy is a procedure used to allow patients to take medications to which they are allergic. The patient is exposed to small but increasing amounts of the known allergen over a period of time to decrease the patient’s sensitivity to the drug (desensitization). This gradual exposure decreases the patient’s risk (or severity) of an allergic reaction to the medication.

In an allergic reaction, the body mistakes a harmless substance, in this case a medication, for a dangerous invader. It launches an attack that leads to the allergy symptoms. Allergic reactions usually do not occur with the first exposure to the drug because it takes time for the immune system to produce antibodies to react to the medication. This process is called sensitization.

For people with diabetes, insulin allergies, though uncommon, may require drug desensitization therapy. All diabetic patients develop some antibodies to insulin. For most, the level is too low to cause problems with management of glucose (blood sugar). In rare cases, however, a person may have a strong allergic reaction to insulin that usually manifests in one of two forms:

• Local reaction. This reaction is limited to the injection site. Symptoms include red and itchy skin.
  
  
• Systemic reaction. This is a reaction that affects the entire body. Symptoms include hives, red patches across the body, heart palpitations and breathing difficulties.

Insulin allergies may be associated with antibodies that neutralize the medication or make it less effective. In some cases, antibodies affect the amount of time it takes for insulin to work. Insulin reactions are more likely to be triggered by animal-based insulin, which is seldom used, than by synthetic human insulin.  In some cases, impurities in insulin may cause a reaction. Inhaled insulin was found in recent research to produce a greater antibody response than injected insulin but was not found to increase allergic reactions.

When a patient is allergic to a specific medication that offers the most effective treatment for a condition, desensitization may allow the patient the benefit of the treatment but without severe allergic reactions. Insulin desensitization is commonly performed using synthetic insulin with a rapid desensitization protocol, an increased time frame in which desensitization is achieved in a matter of hours or days.

Physicians usually determine whether a patient is a good candidate for desensitization through determining the:

• Patient’s general health
• Specifics of the patient’s allergy history
• Type and severity of allergy symptoms
• Results of allergy tests
• Necessity of the medication to the patient’s immediate health

The state of the patient’s health is always a consideration because ill health can make an allergic reaction very hard on the body. Other complications could occur because the body is already in a weakened state.

Severe allergic reactions, including anaphylaxis (reactions affecting two or more body systems), are sometimes possible during drug desensitization therapy. Patients at risk for such reactions may not be candidates for desensitization. In such cases, patients will need to consult with their physician about alternative forms of therapy – for example, switching from beef/pork insulin to human insulin, or taking drugs such as corticosteroids, a class of anti-inflammatory immunosuppressives, to reduce antibody activity.

People may experience allergic reactions to nearly any medication, but there are usually many alternatives, making desensitization unnecessary.

However, there are no alternatives to insulin for people who need it. Drug desensitization is important to eliminate allergic reactions with these individuals to allow the continued use of insulin.

Insulin allergies are rare. More commonly desensitization is used in people who are allergic to specific antibiotics. Penicillin allergy is the most common type of drug allergy, and these allergies can occur in association with many related antibiotics. For most people, a physician can prescribe other antibiotics unrelated to penicillin. In some circumstances, however, penicillin is the best drug to prescribe, and only under these conditions would desensitization be recommended.

Desensitization may be beneficial for people allergic to aspirin, a common pain reliever and anti–inflammatory drug widely used to prevent heart attacks and stroke in people at risk of heart disease, such as diabetes patients. However, not all people with heart disease and aspirin allergy are candidates for desensitization because success depends on the severity of the allergy.

Before beginning drug desensitization, a physician will first determine which drug may be causing the allergic reaction. A battery of allergy tests may be needed to ensure that the suspected drug is in fact responsible for the 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.
  
  
• Allergy blood tests. A sample of the patent’s blood is tested for substances that indicate an allergic reaction has occurred to a specific allergen.

If an allergy to insulin is suspected an anti-insulin antibody test may be performed. This blood test measures the presence of antibodies against insulin and can diagnose insulin resistance or allergic response to insulin. If an allergy reaction is evident, the physician may recommend desensitization therapy.

Drug desensitization therapy takes place in a hospital or clinical setting for the patient’s safety. The patient may be required to spend one or more days in the hospital. Patients should ensure that they have a ride home as they may not feel well for a short time after therapy.

It is likely that skin testing with a tiny amount of insulin will be performed to ensure that the patient does not have a serious, potentially life-threatening reaction to insulin.

Desensitization time for other allergies varies with the patient’s condition. Drug desensitization therapy typically takes place over hours or days. This increased 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 insulin typically takes place over a matter of several hours or several days. The patient will be exposed to small amounts of the allergen every 10 to 30 minutes, which will be gradually increased over time.

The patient is introduced to small but increasing amounts of the drug. The method of drug desensitization is determined by the type of drug, allergic symptoms and other factors. For insulin desensitization, injection is the most likely method to be used, with doses given either subcutaneously or intravenously. 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 rapid desensitization therapy procedure and will be monitored for some time after each dose to ensure that a significant allergic reaction is not occurring.

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.

What follows the drug desensitization therapy depends on the drug allergy, the patient’s condition and other factors. Those who have been desensitized to insulin are likely to be tested to see if their blood reveals lower antibodies to insulin than were present before the procedure. Some patients can go home right after the therapy, but others will need to stay for some time to be monitored by the physician.

Patients should ensure that they maintain the best state of health they can after therapy. Adequate rest, good nutrition, exercise and adherence to the diabetes care plan and sick-day plan are important. These measures will help boost the immune system and be beneficial overall. Patients should stay in contact with the physician and raise any issues when necessary.

Desensitization is usually recommended only when a patient's health requires the use of a specific drug for which there are no adequate substitutes, such as insulin. The main risks of desensitization include:

• Therapy failure. Drug desensitization therapy is not effective with all medication or for all patients. If the therapy does not work, alternative (if less effective) therapies may be needed to control the medical condition.
  
  
• Severe reaction. Whenever allergic people come into contact with the allergen to which they are sensitive, a severe allergic reaction is possible. The risk is higher with drug allergies, which is a common trigger of anaphylactic shock. Desensitization should take place in a clinical or hospital setting under the supervision of an allergy specialist (allergist or immunologist).

Other considerations are the state of the patient’s health. Exposure to the allergen during desensitization may cause an allergic reaction. If a patient is in poor health, then even minor reactions could pose significant health risks. The risk of causing an allergic reaction may outweigh the potential benefits for patients with heart problems or life-threatening conditions.

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about desensitization therapy:

1. Do I have an allergy to insulin or other medication?
   
   
2. Am I candidate for desensitization therapy?
   
   
3. Are there any alternate drugs or other treatments I can use to avoid the need for desensitization therapy?
   
   
4. What are the possible risks of desensitization therapy to me?
   
   
5. What are the possible risks to me if I don’t undergo desensitization therapy?
   
   
6. Where would I undergo desensitization therapy?
   
   
7. How long would I be there?
   
   
8. What should I expect during desensitization therapy?
   
   
9. Will you monitor me, or will another doctor?
   
   
10. What will be done if I experience anaphylaxis, anaphylactic shock or another problem?
    
    
11. What sort of follow-up care will I receive?