ANAPHYLAXIS

Please see the section on the basic Allergic Process in the Allergic Respiratory Diseases section before continuing here. As previously explained, anaphylaxis is a serious generalized reaction that occurs when mast cells and basophils release their chemical contents in response to allergen or other substances (i.e., ASA, NSAIs, IVP dye, etc.). These chemicals when released result in swelling, fluid accumulation, bronchoconstriction (the tubes in the lungs narrow), decreased blood pressure, or shock (no blood pressure). A thorough discussion of anaphylaxis would require a full book, but I would like to touch on what I feel are the important aspects. A definition of anaphylaxis that fits every situation is difficult, however, I like to think of anaphylaxis as a serious reaction that involves either 2 or more systems (the skin, respiratory, cardiovascular, nervous, gastrointestinal systems) or involves a single system reaction that is extraordinarily severe. It is difficult at times to tell the difference between a simple allergic reaction (for example, developing hives) and anaphylaxis. The history is critical in determining if another system was involved. Feeling extremely weak could represent either low blood pressure or anxiety. Chest tightness could represent a mild asthmatic reaction or anxiety. If there is a possibility that 2 systems were involved in the reaction, it should be assumed that this represented anaphylaxis. Although, there are systems that grade severity of reaction, I feel the only useful solution is to determine from the history whether this was a mild reaction or a severe life threatening reaction. If allergy is suspected of causing the reaction, every attempt should be made to prove the suspect allergen was the cause. For example: if allergy to peanuts was suspected, skin testing should be done to prove this allergy, and usually the skin testing is very positive for a substance causing anaphylaxis. The testing should take into account the severity of the original reaction, and be performed in the safest possible manner (if the reaction was severe, a very dilute small amount of test material should be used for skin testing). Only in extraordinarily severe cases should the suspect allergen be assumed without confirming this allergy by testing. In cases of anaphylaxis not caused by IgE, type 1 allergy, usually the only way to prove the suspect agent was the cause is to challenge the person with the suspect agent. Needless to say, this must be done extremely carefully, starting with extremely small exposures, done in a facility that can treat a severe reaction, and with the full understanding and consent of the person involved. ASA and it's related compounds the NSAIs are a good example of this kind of problem. In this case, ASA directly causes the mast cells to release their chemicals, skin testing is of no benefit, and challenge is the only way to prove it caused a reaction. To prove that ASA caused an anaphylactic reaction requires careful consideration of all aspects (the severity of original reaction, the need for ASA in the future, the health of the anaphylactic person, a complete understanding of all risks involved, etc.). The bottom line still is that if at all possible the cause of anaphylaxis should be independently proven so that unnecessary avoidance is not carried on for the rest of someone's lifetime. The list of specific things that can cause anaphylaxis grows daily, virtually any food or drug can be involved, and you should assume any substance can cause anaphylaxis.

Various points to remember about anaphylaxis are listed below:

- usually the onset is rapid, often within seconds to minutes, and delayed reactions are uncommon

-the initial symptoms often involve the skin, tingling or numbness, particularly of the face-neck area, rapidly followed by itching in the face-neck area, under the arms, in the groin, or all over

-itching is often rapidly followed by hives (itchy bumps developing that can vary in size tremendously and also vary in color (white to red))

-larger swelling (angioedema) can develop in the skin, mouth, throat, airway, or bowel (possibly pain, nausea, vomiting, diarrhea)

-generally the more rapid the onset and the more systems involved the more severe the reaction

-clear breathing difficulty (either swelling narrowing the airway or bronchoconstriction-wheezing-asthmatic response) or low blood pressure (feeling very weak and faint, pale, sweating, rapid fast pulse) indicate a severe reaction

-injectable epinephrine (adrenalin)-EpiPen TM (EpiPen registered Trade Mark)( www.epipen.ca ) -is the treatment for anaphylaxis, given into the muscle (usually the outer upper thigh). Another injector Allerject TM is not available at this time (this may become available again).

-the earlier epinephrine is administered the better the chance of controlling the anaphylactic reaction (many fatal cases involve people not giving themselves their epinephrine early on in the course of a reaction ,i.e. trying to wait and see) AND early administration reduces the risk of a delayed reaction (secondary-LPR). Epinephrine given into the thigh begins to work within 3 minutes.

-epinephrine can be repeated in 15 minutes if necessary (in severe reactions, not responding to initial epinephrine it can be given in five minutes)

-high dose antihistamines should be taken by mouth as soon as possible after epinephrine administration, but can take 30-60 minutes to work and will likely not help in severe reactions (in persons with a history of severe anaphylaxis, consideration should be given to pre-exposure treatment with an antihistamine and oral prednisone available to use immediately after epinephrine)

-immediate transport to an emergency department or immediately call an ambulance. In cases of collapse (low blood pressure, shock), lie the person flat and elevate legs.

-the majority of fatal cases of anaphylaxis involve a severe asthma attack, thus having pre-existing asthma is a marker for severity of anaphylaxis, and an asthmatic who is anaphylactic must have their asthma well controlled at all times (by anti-inflammatory medication) as poor asthma control increases the risk of fatal anaphylaxis.

-all anaphylactic persons must have a readily identifiable Medic Alert TM (Medic Alert registered Trade Mark) (www.medicalert.ca ) or similar bracelet-pendant on their person at all times.

-as soon as a child is capable of carrying their own EpiPen TM, they should. Epinephrine containing devices are useless if locked up in the teacher's desk, principal's office, etc. Tough pouches are available to protect the EpiPen TM.

-I always recommend an antihistamine be kept with the EpiPen TM; in older children and adults-wrap the antihistamine tablets in cellophane and put under the container screw on cap; in young children have a small plastic bottle containing the exact dose of liquid antihistamine, taped to the outside of the EpiPen TM container. In general, double the standard single dose of antihistamine should be given. Antihistamines are helpful for mild allergic reactions and may help with some symptoms in an anaphylactic reaction, BUT early injectable epinephrine is the treatment for anaphylaxis.

-every person who is anaphylactic MUST demonstrate to me with a "dummy EpiPen TM" exactly how they would use it. The majority of individuals who own an EpiPen TM do not know how to correctly use this device, and when asked to demonstrate correct technique fail miserably. If you don't know how to use this device under relaxed conditions, you sure as " won't use it correctly under emergency conditions. Mentioning a few pointers is worthwhile: firmly hold the EpiPen TM in the palm of your hand with fingers wrapped around the middle of the pen (don't just use your fingertips, this increases the risk of you dropping the pen), get ready with the pen over your outer upper thigh before you remove the top safety cap (I have had many patients remove the safety cap to early and accidentally touch an object (i.e. coat, jacket, wall, etc.) and the pen discharges), firmly strike the outer upper thigh at right angles ( 90 degrees) with the tip of the pen, and hold the pen in that same position for five full seconds to allow the epinephrine to be injected into the muscle.

-anaphylaxis to hymenoptera venom (honey bee, wasp, hornet, yellow jacket) deserves a few pointers also. These insects are attracted by any bright color (white, yellow, orange, red, etc.) -they think you are a flower AND also by the color black (not commonly known). The colors green and brown are neutral to these insects. Individuals anaphylactic to hymenoptera should only wear green and brown clothing outside during the insect season. This significantly reduces the risk of sting. Insect repellant (containing DEET) used for mosquitos and black flies does not have any effect on hymenoptera. Scents also attract hymenoptera (again, you smell like a flower). You should not wear any perfume, cologne, scented deodorant, scented shampoo, etc. when outside. Lastly, food attracts hymenoptera. Any food will, but carbonated sugar containing drinks are particularly bad. No individual anaphylactic to hymenoptera should drink from a pop can in the outdoors. Last year alone, I had three patients stung inside the mouth by hymenoptera after drinking from an outdoor soda can (the insect gets inside the can and cannot be seen). Any outdoor beverage should be in an open glass.

-a special mention should be made about the late phase reaction (LPR) or the delayed reaction. An individual who has the initial anaphylactic reaction (the early phase or acute phase reaction) can occasionally have a second reaction (caused entirely by the first exposure that caused the initial reaction). This reaction is caused by the inflammatory cells that are attracted to the reaction areas in the body by the initially reacting cells (mast, basophils). This LPR usually occurs within 6 to 12 hours of the initial anaphylactic reaction / exposure. Because this reaction is caused by different cells, it must be treated with corticosteroids in addition to epinephrine and antihistamines. Every individual who has had an anaphylactic reaction should be observed in the emergency department for 12 to 24 hours so this LPR can be adequately and quickly treated. The fact is, that most emergency departments send the patient home as soon as the individual begins to look better. If you have had an anaphylactic reaction previously with a subsequent late phase reaction, you must stay in the emergency department for 24 observation. I have had patients sent home from the emergency department immediately, even though they have told the emergency room staff they have a history of late phase reactions. If you are sent home early, I advise every patient to have extra epinephrine (adrenalin) on their person, to have a full dose of antihistamine in their system, and to stay within 5 to 10 minutes transport of the nearest emergency department for 24 hours. You must understand this concept and always be prepared to treat a LPR.

- with food allergies-anaphylaxis, remember, in Canada, food labeling is not necessarily all inclusive. Never assume because a specific ingredient is not listed on a label, that the suspect food is not there. Although most manufacturers try to be careful, particularly about nuts, never assume labeling to be accurate. In general, highly processed foods, sauces, etc. should be avoided. Buy basic foods and cook at home. Similarly, never trust a restaurant to avoid a specific food you are allergic to. Many restaurant employees do not know exactly what is in the food they are serving. If you eat at any restaurant, keep the foods eaten as basic as possible (i.e. steak&potato), avoid sauces, and always be prepared to treat an allergic reaction. Consider taking an antihistamine before eating at a restaurant.

-see my downloadable/printable handout on the EpiPen TM to review when and how to use

A major problem with anaphylaxis is dealing with the stress-anxiety that this creates. Many parents are severely stressed by having an anaphylactic child. On the other side of the coin, many individuals as they grow older (particularly teenagers and some adults) do not have proper respect for their condition, don't carry their EpiPen TM or Medic Alert TM bracelet,etc. There are a large number of individuals in our society who have anaphylaxis and do not even know it. They've had a reaction or did not feel well upon a certain exposure and they merely avoid that particular exposure again without ever considering what was happening. Most anaphylactic reactions are not fatal. However, at the opposite end of this argument, is that virtually all anaphylactic reactions are preventable and / or treatable, yet individuals still die every year. I feel the solution to these problems is usually very straightforward - education. If an individual is terrified of anaphylaxis or disregards anaphylaxis, repeat visits with full education is the best way to correct these problems. Continued education to the point the individual feels competent to deal with the situation and understands the possible consequences offers the best long-term outlook. Dr. Sweet 2017