a special program of the National Emergency Medicine Association (NEMA)

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Week: 576.6

Guest: Dr. Marshall Plaut

Topic: Allergies....what we know...

Host/ Producer: Steve Girard

NEMA: Oh, what many of us would do to avoid the allergy season...maybe take a leave of absence and visit a place without the allergens that make us stuffy, sneezy, grumpy...and with some medications, dopey. Well, allergens are everywhere...we have to deal with it...and we're talking with Dr. Marshall Plaut, Chief of the Allergic Mechanisms section of the National Institute of Allergy and Infectious Diseases, about treatments...and what I've always wanted to know - Why are we allergic?

PLAUT: Why we're allergic, we really don't know. But an allergy is probably easiest stated as an inappropriate response to the body who substance is generally harmless. The body, for reasons we don't fully understand, treats the substance as harmful and makes an antibody response to it. When we are re-exposed to the substance which is called an allergen, the combination of the allergen and the allergic antibody triggers a series of reactions leading to the release of powerful chemicals. And those chemicals can cause swelling, congestion, inflammation...which are the characteristics of an allergic reaction.

NEMA: What are the most common things that we are allergic to?

PLAUT: The things we are allergic to are basically proteins. They're called allergens because they have the ability to have us make an IGE antibody or an allergic antibody response to them and the most common allergens are those that we breathe in and they are ragweed pollen, grass pollen and tree pollen are probably the commonest ones. There are also several allergens that we breathe in that are predominantly found indoors such as house dust mites, cat and dog, and cockroach. In addition to those things there are a substantial number of people who are also allergic to foods such as milk and eggs which predominantly occurs in childhood allergy and but also some other substances such as peanuts, tree nuts, shellfish and other fish.

NEMA: What is the range of symptoms?...and how can you tell it's not a cold?

PLAUT: The symptoms are nasal congestion and swelling, mucous production, sometimes a cough and post nasal drip...especially if the sinuses get involved. They are not that readily distinguishable from a cold. The major distinction is the duration and sometimes the severity usually the symptoms are worse than a cold. You lack some symptoms of a cold, you don't usually get a fever despite the term hay fever, people with allergies don't get fever. And they also may get worse symptoms and they last longer then ten days to two weeks that people with colds have.

NEMA: If you have an allergy, are you predisposed to having others? And do they team up to make symptoms worse?

PLAUT: Allergy is primarily a genetic disease and most people who are allergic are allergic to a whole series of proteins. There are a lot of people who are allergic to cat and dog and dust mite and ragweed and grass and trees. It's actually, certainly is common to being allergic to one of them. Clearly there are people who are more allergic to one thing than another. We do not know whether or not being sensitive to one early in life makes you specifically...changes the pattern by which you become sensitive to something else. There is a sequence that, in young children who are allergic, tend to be allergic to foods before they become allergic to the inhalant materials. The question is, for example, can you prevent the development of allergy to inhalants by preventing people from becoming allergic to foods, by not exposing them to food. And there's a little bit of research suggesting that that may be true, but at the moment it's unproven whether there's a sequence, and if you stop the sequence you can prevent the rest of it from occurring. There similarly a little bit of data in children, that if when you catch children very early in life and they're allergic to let's say one thing, like grass pollen, and if you treat them with immunotherapy shots...that you may reduce their likelihood of becoming allergic to something else. So those are both very attractive ideas, but we just don't have enough data to be certain that that actually occurs. If you are allergic to two things, like for instance ragweed and cats, then the combination of the two are going to be much worse then one alone. In other words, people who can tolerate a cat most of the year...during the ragweed season - if they're allergic to ragweed - may find the combination of the symptoms overwhelming and don't tolerate the combination of cat and ragweed...where they tolerate either one alone much better. One other thing that's worth knowing and that is that some proteins in apparently unrelated substances, proteins can be very related. For example, people who are allergic to a protein in latex rubber may also be allergic to certain proteins in certain fruits, like kiwi fruit, and therefore they might find they get reactions to both. It's actually because of there's only one sensitivity...but it happens to be the protein they're sensitive to is present in both products, both latex and the fruit.

NEMA: I see many people walking around this time of year with heavy head congestion, sneezing...the works. And they refuse to take medication for it....

PLAUT: There are medications around that will effectively relieve symptoms so that there's no reason to suffer if necessary. Over the counter medications work for people with mild symptoms, but if the over the counter medications are not working, or the symptoms are severe...then it's worth seeing a physician cause there are a series of treatments available for mild and severe allergic disease such as nasalcromal, nasalcorticosteroids, or immunotherapy allergy shots and some other things...which in combination are or separately may give very dramatic relief even for people with very severe symptoms. The question is are their symptoms bothering them and are they affecting their quality of life. Is it causing you to miss work, to miss school or perhaps are likely to miss recreational activity like going on a picnic or playing ball.

NEMA: I've had what's called 'rebound' in the past...can you explain it?

PLAUT: Rebound is a phenomenon that occurs where one medication, when its affect wears off, your symptoms go back to where they were before, or even to worse then what they were before you took the medication. Rebound...usually we talk about decongestants, especially internasal decongestant sprays, where typically the decongestant will, in fact, constrict blood vessels and relieve the congestion in the nose... but after a few hours, when the effect wears off, you may actually get worse swelling than you had before. And sometimes the rebound is such a major problem that you need to get to the doctor to take another medication to stop this rebound affect from decongestants.

NEMA: What about the process of immunotherapy?

PLAUT: What the process involves doing is injecting into the muscle small amounts but increasing amounts of the material you're allergic to. The immune response to the allergen is changed over the natural exposure, where you're not getting it intramuscularly, you're getting it inhaled...and the effect to that altered immune response is to relieve your symptoms. How long you need to take it and when it's safe to stop varies from person to person. And also, although it is effective, it takes a while to be effective. You may not see maximal benefit for a whole year.

NEMA: I had a slew of allergies, and have lost most of those sensitivities...what cause us to gain or lose allergies over time?

PLAUT: Many people who don't do anything differently find that there are typically cycles in terms of what allergy symptoms are worse. Not to put exact ages on this, but often children will be worse from ages 6 to 12 and get better in teenage years, get worse again in their early twenties, and then get better. Some people get worse again in their early thirties and then get better. Often the allergic antibodies to persist but that the symptoms that are produced by this chemical reaction with the allergic antibodies is just less severe for reasons we don't understand.

NEMA: Where is the angle on current research now...and what might be coming down the road that might give more relief?

PLAUT: I suppose the most exciting thing is to look at the genetics of allergy. As I say allergy and asthma are clearly have a major genetic component and the science has advanced to the point where there are several, where we've identified regions where genes appear to be whose abnormalities are associated with allergy. We haven't identified yet which specific gene abnormality is associated with it but probably some of those genes have to do with why the inhaled substance induces an allergic response and others have to do with subsequent events following sensitization that lead to symptoms. We certainly haven't sorted that all out. The exciting thing is that the science of genetic analysis is such that within a few years where it's very likely that we will have identified very specifically the gene itself, not just the region of the chromosome, where the genes themselves....and may well be able to identify which specific genes are abnormal in any one person with allergy. There may well then turn out to be a very specific treatments.

NEMA: Our thanks to Dr. Marshall Plaut, Chief of Allergic Mechanisms section of the National Institute of Allergy and Infectious Diseases.

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NEMA: Thanks for joining us for today's program. If you have any comments or suggestions, contact this station. Or visit our home page at: www.nemahealth.com/ ...for a look at transcripts of this or past programs, or to find out more about the National Emergency Medicine Association. I'm Steve Girard at The Heart of the Matter.



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