The Asthma Center


Anaphylaxis is a severe, potentially life-threatening allergic reaction that can affect many parts of the body. Skin symptoms are most common and can include hives, itching, swelling, tingling, flushing and redness. Other common symptoms can include lip, tongue or throat swelling, and gastrointestinal symptoms such as nausea, vomiting, diarrhea and abdominal cramping. Women can occasionally experience uterine contractions mimicking the pain of labor. Upper respiratory symptoms include itchy eyes and nose, congestion and post-nasal drip. Chest symptoms include shortness of breath, coughing and wheezing. In addition, circulation related complications can include a significant drop in blood pressure that can lead to feeling faint or blacking out.

Anaphylactic reactions can be triggered by stinging insects such as bees, wasps, hornets, yellow jackets and fire ants; foods including milk, eggs, fish, shellfish, tree nuts, wheat, peanut and soy; medicines such as antibiotics (particularly penicillin and penicillin derivatives), aspirin and other aspirin=like amedicines (non-steroidal anti-inflammatory drugs); latex which is often found in household items such as elastic waistbands, balloons, kitchen gloves and condoms; and, rarely, exercise which may or may not be dependent on certain food ingestion prior to exercise. In 20% of cases, the cuase of anaphylaxis is unknown, and this condition is called idiopathic anaphylaxis.

Anyone can experience anaphylaxis. It is estimated that 5% of the population in the United States experiences anaphylaxis annually, and 15% of individuals in the United States may be at risk for developing anaphylaxis. Although anyone can develop anaphylaxis, those with a history of allergic diseases such as hayfever, asthma and/or eczema or who have experienced an anaphylactic reaction in the past are at greater risk.

The signs and symptoms of anaphylaxis often occur suddenly, though some reactions may take several hours to develop. Fortunately, most symptoms can be controlled with appropriate medication, but if symptoms are not controlled, the reaction may progress quickly and become life-threatening. It is for this reason that any individual who has experienced or is at risk for an anaphylactic reaction should have an epinephrine autoinjector available with him/her at all times.

Epinephrine, also known as adrenaline, is a natural hormone that the body produces in response to stressful situations. This is often called the "fight or flight" response. The epinephrine taken as medicine works exactly as the epinephrine the body produces. Administered epinephrine can therefore increase heart rate and blood pressure, relax the airways in the lung and can stop swelling reactions in tissues and skin. These positive effects can temporarily half the life-threatening effects of an anaphylactic resonse. Epinephrine, like most medications, has side effects. These include: increased heart rate, a feeling of nervousness, pale skin, headache and/or shaky hands. Occasionally a severe irregular heart beat can occur. The benefits of using epinephrine in a lifei-threatening anaphylactic reaction always outweigh these potential side effects.

The epinephrine autoinjector, about the length of a magic marker, is available in 2 doses made for different body weights. For those 66 lbs or under, the dose is 0.15 mg and the0.3 mg dose is for those 66 lbs or more. The needle in the device is protected inside the autoinjector pen and is released upon pushing the autoinjector against the outer part of the thigh. The needle has been designed so that it can penetrate clothing.

Although antihistamines and oral corticosteroids are often administered during an anaphylactic reaction, epinephrine is the only drug that will actually reverse an anaphylactic reaction, and therefore epinephrine is the drug of choice for anaphylaxis. Antihistamines will typically help symptoms within an hour, and oral corticosteroids may take even longer. Therefore, the immediate and potentially life-threatening nature of anaphylaxis will not necessarily be relieved by use of antihistamines and corticosteroids alone.

An estimated 1000 individuals die from anaphylaxis each year. Often, death is due to either a delay in giving epinephrine or not administering it at all due to fear of the medication or due to lack of availability. When there is any doubt as to whether or not to use epinephrine in the context of anaphylaxis, it is usually better to use it due to the potentially dire outcome if this medication is witheld.

About 25% of individuals who experience anapylaxis may have a second wave of symptoms that requires taking a second dose of epinephrine. This second reaction may occur up to 72 hours later, and therefore individuals who have a history of anaphylaxis should have multiple doses of epinephrine available. The epinephrine autoinjector should be stored as close to room temperature as possible. The device should not be left in extreme hot or cold temperatures or indirect light which can change the epinephrine effectiveness or cause the autoinjector to malfunction. The liquid inside the device should always appear clear. Epinephrine has an expiration date, so it is important to check the date and make timely renewals. Epinephrine that is out of date or goes bad will discolor and darken. When receiving epinephrine from the pharmacy, it is important to check the expiration date and make sure the autoinjector will last at least 12 months.

Currently there are 2 autoinjector devices commercially available, which have the same medication, but the injector mechanisms work in different ways. It is important to be familiar with whichever device is prescribed. The EpiPen device has a single dose of epinephrine and can also be purchased as a 2-pack with 2 doses of epinephrine which should not be split apart. Twinject is the second product which has 2 doses available in the device. The first is administered as an autoinjector, similar to the EpiPen(TM). The second dose is carried in the device and can be manually injected into the skin.

Disposal of a used or expired epinephrine device should be done through a medical facility where it can be disposed of properly.

Understanding the triggers and symptoms of anaphylaxis, use of an epinephrine autoinjector, and knowing what to expect after using epinephrine should give at-risk individuals confidence and comfort when responding to an anaphylactic reaction.