Patients who have been approved to undergo immunotherapy will first need to pinpoint the allergen to which they react. This is usually accomplished through an allergy skin test, in which small amounts of one or more allergens are introduced to the skin, and through blood tests.

Once an allergen has been identified, the first allergy shot is scheduled. An individual preparing to undergo immunotherapy may be advised to take the following precautions:

• Avoid exercise for two hours before an appointment
  
  
• Inform physician of all current medications, especially beta blockers (used in the treatment of heart-related problems or high blood pressure) or monoamine oxidase inhibitors (used in the treatment of depression)
  
  
• Tell physician about pregnancy or plans to become pregnant

Because patients risk severe reactions after receiving an allergy shot, the treatment should be administered only under the supervision of a physician who is trained in immunotherapy and prepared to treat potentially life-threatening emergencies.

During the first session, a solution of diluted salt water (saline) is combined with a very small dose of the allergen. This is injected under the patient’s skin, usually in the back of the upper arm. Patients who fear needles can be reassured that allergy shots are much less painful than the deep, intramuscular injections given during standard immunizations. The needles used in allergy shots are very fine-tipped, and they are injected just below the skin’s surface rather than into the muscle.

After the first injection, the physician monitors the patient for about 30 minutes to make sure no allergic reaction or other symptoms occur. In very rare instances, a whole-body allergic reaction known as anaphylaxis can occur. Left untreated, anaphylaxis can quickly progress to life-threatening anaphylactic shock, which is characterized by difficulty breathing and a dangerous drop in blood pressure. If this rare reaction occurs, the physician may administer a dose of epinephrine, corticosteroids and intravenous (I.V.) fluids, which usually reverses symptoms rapidly.

Those who suffer from asthma should also be sure to carry their rescue medication (e.g., bronchodilator) with them in case respiratory symptoms develop following an injection.

Patients may experience other, far less dangerous, symptoms during an immunotherapy session. These include:

• Redness or flushing
• Warmth of skin or hot flashes
• Mild itching
• Slight swelling at the shot site

Such mild symptoms usually disappear within four to eight hours. A physician may recommend cold compresses, oral antihistamines or topical corticosteroids to relieve these symptoms.

Patients who do not have a reaction to the trace amount of allergen are likely to be discharged until the next treatment session. Though anaphylaxis often begins immediately after an individual has been exposed to a particular allergen, it can sometimes occur several hours after exposure. If patients have a reaction after leaving the medical facility, they should immediately return to the facility or visit an emergency room. Many allergists also prescribe an allergy kit in case a reaction occurs after leaving the medical facility.

After the initial injection, a patient will return for periodic follow-up treatments. Though the frequency of follow-up injections varies depending on the physician, these injections typically take place once or twice a week over the course of several years. With each successive treatment, the amount of allergen injected under the skin is increased, and the body gradually is desensitized to the allergen.

Patients who experience an anaphylactic reaction after receiving an allergy shot typically continue treatment. However, the subsequent injection will contain a reduced dosage of the allergen. This helps the patient’s body build up its immunity more gradually.

After about six months, some physicians reduce the injection frequency to once a month (known as a “maintenance dose”) for three to five years. At this point, some patients no longer need shots and are symptom-free for years. If symptoms return, the injections begin again.

It is important for patients receiving allergy shots to keep all of their immunotherapy appointments. The treatment method is successful only when the shots are given on a predetermined schedule.

Immunotherapy patients generally do not notice great improvement right away. It can take up to a year before they notice any significant change in symptoms.  During the second year, substantial improvements should be evident. When an improvement is not seen after a year of maintenance therapy, physicians will look for possible factors interfering with the treatment. These may include inadequate doses of the allergen or failure to identify allergens during initial allergy testing. When such a factor cannot be found, physicians may choose to discontinue immunotherapy and pursue alternative treatment options.