Your Questions Answered: Anaphylaxis
In our October webinar, Dr. Robert A. Wood, a professor of pediatrics and chief of Pediatric Allergy and Immunology at Johns Hopkins, and professor of International Health at the Johns Hopkins Bloomberg School of Public Health, focused on anaphylaxis, a severe allergic reaction that is potentially fatal.
Dr. Wood, who is also a member of FARE’s Medical Advisory Board, discussed the risks, symptoms and treatment of anaphylaxis; dispelled myths; and answered questions from the audience. Dr. Wood’s full presentation can be viewed below or on our website, but here are his responses to some of the questions submitted by audience members.
- How can you distinguish between symptoms of anaphylaxis and other illnesses? (e.g., asthma attack, random hives, stomach cramps, or anxiety attack)
The symptoms can be identical. What we want to do is interpret the symptoms in the context of the overall situation and the chance that there’s been a food exposure. So if your child gets random hives or stomach aches and they’ve been home for the last several hours, and you know what they’ve eaten, and you’re confident they’ve not had an exposure; you can be quite confident these are random hives or stomach cramps. On the other hand, if you’re out at a family party for the holidays, and the food has not been under your complete control, and they show up with these same symptoms, we would be more worried that this may indicate a food exposure and the beginning of an anaphylactic reaction.
- Are there any clear differences in the way anaphylaxis progresses in children versus adults?
The overall answer is no. The thing that does change is that as people get into middle age they’re actually more prone to the cardiovascular or blood pressure effects of an allergic reaction. One reason we don’t see blood pressure being the cause of death in children is that the heart and blood pressure systems in kids and young adults is very strong and typically can keep going in spite of a reaction. But as we hit middle age and older, our blood pressure system may not be as sturdy, and adults in that age group will be more prone to have the low blood pressure or anaphylactic shock.
- Is there any way to find out how much allergen it would take to cause an anaphylactic reaction in our child?
We generally don’t have a clear answer to this. With the patient who comes in and has had 10 or 15 or 20 reactions, we can carefully look at each of their exposures and be able to say, “Okay, with this reaction, with this much exposure and that’s how they reacted.” Otherwise I cannot look at a test result, I cannot look at a prior reaction or two and make any real prediction about what the reaction will look like or how much allergen it will take to cause that reaction. Some people want to undergo formal food challenges to get this answer. In a food challenge, we’re obviously intentionally feeding someone what they might be allergic to, and many times inducing an allergic reaction. But it is not designed to answer the question posed here, which is how much allergen it would take to cause an anaphylactic reaction. It doesn’t answer that because when we do a food challenge, we stop the challenge at the first sign of the reaction. We don’t push it to say, “How much more would it take to lead to anaphylaxis?” That would not be an ethical way to practice. So even a food challenge does not typically answer that question.
- If a person is having an anaphylactic reaction and doesn’t respond to epinephrine, is there anything that a hospital can do at that point?
Absolutely yes. Now, there are cases where the reaction has gone too far by the time the patient gets to the hospital that there is nothing more to do. But, if for example someone was still having breathing problems after getting epinephrine, it is possible in those cases to put a breathing tube in place or to put a tracheotomy in place to make sure that air is still being provided into the lungs to maintain breathing. If someone is having low blood pressure because of their reaction that epinephrine didn’t stabilize, IV fluids and the use of these other medications can be extremely helpful. So, thankfully in most instances, if we’ve done the appropriate home management of an anaphylactic reaction, the response you get from the emergency room is, “What are you doing here? Your child looks fine.” The truth is that they look fine because you treated them appropriately. In most instances, a single dose of epinephrine along with a dose of antihistamine will completely reverse the reaction. So they do look fine but it doesn’t mean they shouldn’t be there. You want them there for the 20% of the time that additional medications are needed.
- Are people with asthma more at risk of fatal anaphylaxis, and why?
Yes. Because the main reason that people die of anaphylaxis is that their airways shut down. Because of the underlying asthma, your airways are likely to be more sensitive to an allergic reaction.
- Does the risk of an anaphylactic response increase with each exposure to an allergen?
Absolutely not. The next reaction is completely unpredictable. The biggest variable in that next reaction will be the dose of exposure. Since we have no idea what that dose will be, we can’t predict the reaction severity. Think back to the examples I was giving: If this reaction occurred to a contaminated cookie that had 1/100th of a peanut, and the next reaction occurred to eating a full cookie that had well-disguised peanut that had the equivalent of five peanuts in it, that reaction just had a 500-fold higher dose and will be much more severe than the one before. Again, you can’t take any reassurance that the last reaction wasn’t severe. If someone has had a huge exposure with only a mild response, that is a little bit reassuring. But because these allergies can change over time, even that wouldn’t make us say, “Throw away your epinephrine.”
- For people with peanut or tree nut allergies, how dangerous are ball games, airplanes, and other places with lots of nuts?
As a general rule, because ingestion is the main root of exposure that poses risk, being around nuts is not going to be dangerous. Now, airborne reactions can occur. They will typically only happen though if the nuts are being disturbed in a way that will create a dust and if you are in a very confined space. So if you think about how that might happen, you will definitely get more peanut allergen in the air if you’re cracking open nuts, especially if you’re throwing nuts on the floor and walking on the shells. Each of those activities may create some dust that does contain allergen. If you’re in a contained space – if you’re in the waiting area of a restaurant and everyone is cracking open nuts, and the floor of that waiting area has an inch-thick peanut shell on it - that is a place that you could have a dangerous airborne reaction. That same amount of peanut at a ball game, though, virtually never causes problems. In the outdoor air, it’s very rare to see true airborne reactions. Now on airplanes, if everyone was cracking open nuts, airplanes would be a scary place. But the truth is that just by opening bags of peanuts, there’s very little peanut allergen getting into the air. We can’t say that it’s a zero risk situation. I can’t say that ball games are zero risk; I can say they’re very low risk. For me and my peanut allergy, I don’t worry about ball games or flying at all. I have no concern about it whatsoever. If my patients want to avoid ballgames or be on peanut-free flights, I don’t say that’s wrong. Although I think that normalizing life as much as possible and finding a cooperative airline that won’t serve peanuts, at least for peace of mind, may be a reasonable approach to be less anxious and still enjoy a family trip or vacation.
- You have had several anaphylactic reactions. In your own words, can you please describe what you or someone experiencing this type of reaction may be feeling?
I can tell you that I’ve been very fortunate going nearly 20 years since my last anaphylactic reaction. But the memory of my last reactions is still very vivid, so this is something that sticks with you. I can tell you that my reactions, of which I’ve had 5 or 6 in my lifetime in the very severe category requiring epinephrine, one requiring multiple shots of epinephrine, all looked different. None of them looked the same. One had a very abrupt onset, one took 20 or 30 minutes, one had a lot of GI symptoms. All of them thankfully gave me an immediate reaction in my mouth, so I had a warning sign that I was eating a problem food. I was eating a food that was supposed to be completely safe, was promised to be safe, but while I was eating it I recognized that my mouth was itchy and I knew something was wrong. Then I could intervene, obviously to stop eating but also to begin treatment. Since I have this history of severe reactions, I will immediately administer epinephrine; there would be no reason for me to wait at all.
Questions about Treatment:
- Should RAST [blood test] or skin test scores be used to change an emergency care plan? If not, what are they useful for from a severity standpoint?
The answer to the first question is absolutely not. They have no bearing on an emergency care plan. For the second question - they have very little use from a severity standpoint. So these are valuable tests to make a diagnosis. They are problematic even in making a diagnosis, but they are truly not useful in designing your child’s emergency care plan. You can have people with low scores and severe reactions, people with high scores and less severe reactions. If you take a large group, if you took 100 people with peanut allergy, you would see somewhat more severe reactions in those at the very high end of the scale. But you would see dramatic exceptions at either end. Meaning you would see some people at the very high end of the scale who have very minor reactions and some people at the very low end of the scale with very severe reactions. So we have never, and until we get better tests never will, devise our action plan around a test score.
- Can a person's allergy severity worsen to the point that their anaphylaxis plans should change?The answer is absolutely, positively yes. One of the most important things that we do, is every time a reaction happens, we review that reaction. We review it from several standpoints. One of them is we want to think about how it happened – is it a situation that could be avoided the next time? There are always lessons to be learned from a prior reaction that may help the next one. We want to think about what was done during the reaction - was it done consistent with or not consistent with the action plan that we’d established? And was the reaction different than we expected? We may get very good news. We may get news that this child has virtually outgrown their milk allergy because they just got a whole big slug of milk and they barely reacted. That would downgrade their action plan. But more so we want to be in the knowledge of worse reactions to be able to upgrade the emergency care plan to have a more aggressive treatment plan if someone has presented with a more severe reaction than what we anticipated.
- Can antihistamines help after epinephrine is given?
Antihistamines have no life-saving capacity, but they can help. They can help some more mild symptoms. We’ve seen people get epinephrine up front in a reaction, look very good, and then get hives later. I think that giving the antihistamine up front may prevent some of those later hives from happening.
- Is it ever worth giving oral antihistamines if that might mean losing time to administer epinephrine during what might rapidly progress to an anaphylactic reaction?
Clearly, if we knew that reaction was progressing rapidly to anaphylaxis, we wouldn’t wait around and give an antihistamine. But if we’re in one of these situations where we interpret that this might not be such a severe reaction, giving antihistamine at that moment might be very appropriate, while having the epinephrine immediately on hand to administer if the reaction progresses.
We host an educational webinar every month. A recording of our November, “Safely Navigating the Restaurant Scene,” is available on our website here: http://www.foodallergy.org/tools-and-resources/webinars
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