Because immunotherapy involves giving you injections of substances to which you are highly allergic, it is possible that you could have an allergic reaction to an injection. There are generally three types of allergic reactions: small local reactions, large local reactions and systematic reactions.
A small local reaction
A small local reaction is the development of a hive (welt) at the site of injection. This is similar to the reaction to skin testing and is relatively common. The welt is generally smaller in size than a 25-cent piece and goes away within a couple of hours. Small local reactions have little or no significance. If itching is intense, application of ice and use of an oral antihistamine may prove helpful.
A large local reaction
A large local reaction involves development of a large hive (welt) larger than a 25-cent piece and is less common than the small local reaction, There is generally some swelling of the arm that may persist for a couple of days. Local application of ice is used, as well as antihistamines. We may use one or two doses of prednisone to suppress a large local reaction, particularly in persons who have asthma. A large local reaction may be a sign that your immune system is still too allergic to tolerate the dose that is being given. The dose may be adjusted, and the schedule of injections will be advanced cautiously.
Systemic reactions occur very uncommonly, from 1 in 200 injections to 1 in 1.6 million and 1 in 2.0 million. A Systemic reaction generally begins with milder symptoms such as:
- A feeling of “flushing” or warmth all over the body
- Generalized itching
- A sudden sensation of fear or dread
- Itchy throat
- Chest tightness
It is critical, that, if you feel any of these sensations or any other unexpected reaction, you report to the nurse immediately. The antidote for systemic reaction is an immediate injection of adrenaline (epinephrine). All patients receiving immunotherapy should carry an Epi-pen or equivalent on the day of their shot. Your doctor or nurse will provide you with a prescription for one prior to initiating treatment. Systemic allergic reactions are usually reversed immediately once the adrenaline is given. In the event that a systemic reaction develops after you leave the office, the Epi-pen may be used to temporarily reverse the reaction and you should go directly to an emergency room.
Safety Precautions for Persons Receiving Immunotherapy
Check the name and number on the extract bottle before each and every injection to make sure that it is your name and number. In offices, which provide large amounts of extract, it is possible for two people to have the same or similar names.
Always wait in the office in direct view of the nurse and responsible office personnel for at least 20 minutes after an injection. The vast majority of systemic reactions occur during this time period.
Always check your arm at the end of the 20 minute period. If there is a significant local reaction, notify the nurse and she may give you a topical or oral antihistamine. Your next dose may have to be adjusted.
Immunotherapy should not be given on days in which your asthma is not under good control (e.g. peak flow less than 80% of your best or if having symptoms). Similarly, immunotherapy should not be given if you have had bad allergic eye or nose symptoms, or fever. In the event of a acute viral illness, it is best to call the nurse to see if you should receive your injection that day.
If you have any kind of reaction after the immunotherapy injection, notify the nurse immediately.
Do not take beta-blocker medications while you are on immunotherapy. These medications are generally used to control high blood pressure, headaches, or nervousness. They have been shown however to lower the threshold for an allergic reaction, as well as compromising the effect of a life saving shot of adrenaline.
Do not exercise vigorously for at least four hours after an injection. Vigorous exercise can increase the rate at which the extract is absorbed into the body and might lead to a systemic reaction.