December 31st, 2008
Traditional allergy testing is done via skin tests, where a small device often resembling a plastic toothpick is dipped in a well containing an allergen, like ragweed pollen. The skin is then scratched or pricked and observed to see if the area gets red and raised. Most allergists still feel this is the preferred method of testing, but in some cases skin tests just wont work. In these situations, blood tests are a good alternative.
Most people refer to allergy blood tests as “RAST” tests. The term “RAST” is sort of like kleenex or band-aid. It started as a specific term, but has come to be generalized for all allergy blood tests. RAST stands for Radio Allergosorbant Test. This form of testing is actually seldom done, anymore. These days, allergy blood tests are done via Enzyme-Linked Immunosorbant Assay, which goes by the much-easier-to-pronounce acronym, ELISA (ee-LYE-zuh).
To understand these, a little background is needed. ELISA tests measure antibody levels. Antibodies are proteins your body makes to help fight off infection. There are 4 main types, IgG, IgA, IgM, and IgE. The first three are there to help fight off bacteria and viruses. IgE is the allergy antibody.
Each individual antibody is designed to match up with one specific thing, like a lock and key. For example, an IgG antibody might bind to a specific part of the wall of a strep bacterium or cold virus. In allergic people, there are IgE antibodies that bind to ragweed pollen or peanut protein. ELISA tests measure the amount of such antibodies that are present in the blood stream. These are reported as a concentration (kU/L) and as a class or level, arbitrarily class 0-6.
This all brings us to a couple of important points. First, allergy blood tests should be IgE ELISA, not IgG ELISA. Serum IgG testing has no role in the evaluation or management of allergies, be they inhalant, food, or otherwise. I commonly see patients who have been told they have food allergies on the basis of serum IgG tests. Most often, physicians utilizing such tests are also touting non-standard therapies like yeast elimination, detoxification regimens or unproven expensive supplements. Avoid these at all costs.
The second point deals with the interpretation of serum allergy tests. The tests are easy to order- you just draw the blood and check a box. What’s difficult is how to interpret the information. Every test in medicine has false positives and false negatives. With serum allergy tests, the false negative rate is very low, so they are very good at ruling out allergies. The false positive rate is in the range of 5-10%, which is pretty good. So, if you test to 60 different things and get 5 or 6 low level positives, what does that mean? Are they real allergies or not? For Americans used to a black-or-white, yes-or-no, give-it-to-me-straight-Doc world, this ambiguity can be difficult to internalize. A good allergist should be able to interpret these tests correctly and relay the information in a manner which is easy to understand.
Dr. O
December 29th, 2008
I’ll apologize straight away for the groan-inducing headline. Nut allergy is a serious subject and as allergists, we must walk a fine line between imparting the potential seriousness of a reaction and scaring parents into a fear-induced paralysis. A recent study published in the Journal of Allergy and Clinical Immunology, the main U.S. allergy journal, shows that through planning and education, rates of reactions can be lowered considerably.
The study followed 785 kids for an average of about 5 years. All the kids had been seen in a specialty allergy clinic , had written avoidance information and written treatment plans, and had schools which had been educated on how to deal with nut reactions. A few important statistics stood out to me.
First, only 5% of reactions during the study period occurred in schools. This should be reassuring to parents who worry while their children are out of their control and also warns that the majority of accidental ingestions are due to the parents or children themselves.
The annual risk of reaction was about 3%, which is considerably lower than in previous studies. Only 10% of study period reactions occurred in very young kids, <4 years, and 90% of those reactions were mild.
Recent dogma has been that subsequent peanut reactions may be more severe than the initial reaction, but this study found that 90% of reactions were of equal or less severity than the initial reaction. Of those that worsened, only 1 was deemed severe.
All reactions deemed moderate or worse were due to ingestion. Contact reactions were all mild. There were no reports of reactions from inhalation. This should help us further tailor our avoidance recommendations.
The final take home point here is that specialty care is important in cases of nut allergy. Allergists see more cases of nut allergy than other doctors and are specially trained to handle them. Our job is to take the time necessary to educate families on these issues. If you have a child with nut allergy, seeing a allergist is important.
December 17th, 2008
Lets talk for a bit about common allergy medications. In the interest of time, I’ll focus on meds used to treat nasal symptoms, what doctors call rhinitis.
The most common medications used for rhinitis are antihistamines. Antihistamines work, as their name suggests, by blocking the effects of the chemical histamine. They are particularly good for controlling symptoms of nasal itching, sneezing, runny nose, and itchy eyes. They are not very good at controlling nasal congestion and drainage. Older antihistamines like diphenhydramine (benadryl), chlorpheniramine (chlor-trimeton) , and hydroxyzine (atarax, vistaril) are very potent, but they are also very sedating. Newer antihistamines such as cetirizine (zyrtec), fexofenadine (allegra), and loratidine (claritin) are classified as low- or non-sedating and still have adequate potency. I generally recommend one of the newer medications. Cetirizine and loratidine are available over-the-counter and store brands run only about $10 a month.
Decongestants also do what their name suggests: help control nasal congestion. Some people find they help with symptoms of pressure and pain as well. They work by constricting the blood vessels in the nose which, in turn, shrinks the lining of the nasal passage. Since they are oral medications, they will also constrict the blood vessels in the rest of the body, which can worsen blood pressure, In guys, they can also worsen prostate problems. They cause insomnia in a number of people as well. Because of all these side effects, I avoid decongestants as much as possible and limit their use to short periods of time.
Over-the-counter nasal sprays are a double-edged sword. They are sold under a variety of names, but most contain the drug oxymetazoline. They will open your nose like nothing else, but if used improperly can lead to dependence so be very careful with them and always follow the instructions. Never use them for more than 3 days in a row or more than twice a day. If you do, when you try to stop, your nose will be worse than when it started- a phenomenon called rebound. I see patients every week who have become dependent on these medications to breathe through their nose. Don’t become one of them.
Finally, I’ll talk about saline rinse. This is a great treatment for most nasal symptoms, including drainage. It’s essentially free and devoid of side effects. I’m not referring to “ocean spray” that simply moistens the nose, but rather forcing a large volume of saline through the nose. This can be done with gravity-a neti pot- or with force- a plastic squeeze bottle. Either way, make sure you don’t use plain tap water- it’s too dilute and will irritate the lining of the nose. A simple mix involves using a teaspoon of salt in 8 ounces of water. Some companies try to sell you their mix, claiming that they have “pharmaceutical grade NaCl”. This is ridiculous. Plain table salt is fine and could never make the nose a dirtier place than it already is.
Hope this is helpful.
Dr. O
December 15th, 2008
A few weeks ago, I posted on the recent meta-analysis examining the safety of long acting beta-agonists, LABAs. Going by the names salmeterol (Serevent) and formoterol (Fordil), these medications are components of Advair and Symbicort, which also contain inhaled corticosteroids. The FDA recently convened a special advisory panel regarding the safety of these agents, and, fortunately, there were prominent members of the asthma community to advise them along the way. Following the best available evidence and expert opinion, the panel reaffirmed that combination therapy is the preferred choice for adults and children with persistent asthma.
Additionally, they said that LABAs should not be used in isolation, without the addition of an inhaled steroid. For anyone familiar with the literature and with these medications, this is a glaringly obvious conclusion. The scary part is that the FDA had to convene a special panel to resolve internal disagreements regarding the use of these medications. Thanks to those members of the AAP, ATS, and AAAAI who aided in this important decision.
December 11th, 2008
The prevalence of peanut allergy is on the rise in many Western countries, including the US and the UK. This has led to the recommendation that parents delay introducing peanut into the diet. As I touched on in one of my earlier posts, there really hasn’t been any evidence to support this recommendation. Now, a new study out of Britain suggests this may be the wrong thing to do.
The study sent a detailed food questionnaire to thousands of Jewish families in the UK and Israel. In this way the study authors automatically controlled for genetic and socioeconomic differences. The rate of peanut allergy is almost tenfold lower in Israel, .17% vs. 1.8%. The only difference the study authors found was that Israeli children ate peanut much earlier than their British counterparts. Nearly 100% of Israeli kids had eaten peanut by age 12 months as compared to around 25% of the Brits.
This was a very well done study, but it is still only a population study. Prospective controlled trial are needed now to sort out this issue. If a simple recommendation could potentially lead to a 90% reduction in peanut allergy rate, it should be a top priority.
Dr. O
December 10th, 2008
This week’s installment of bogus allergy treatment will focus on the commonly touted remedy of local bee honey. The theory goes something like this: Bees collect nectar to make honey and along the way carry local pollens with them which are then transferred to the honey. Ingesting these small amounts of pollens over time will desensitize the body to them. Sounds great on a superficial level, but this theory is full of holes.
First, most of the pollen bees collect comes from flowering plants, which play little if any role in nasal allergies. Second, many people are allergic to a range of seasonal pollens- tree(spring), grass(summer),and weed(fall) are the three main categories. Honey produced during an individual season may contain pollen present during that time but will not contain other pollen varieties. So if was made in the summer and you took it in the fall, it would not contain fall pollens. Third, oral immunotherapy doesn’t work. (This is distinct from sublingual immunotherapy.) Numerous studies looking at a variety of dosing levels have shown swallowing allergens to have no effect on allergic symptoms.
So maybe its not the pollen at all. Maybe there is something special in bee honey that reduces allergy symptoms. A randomized, placebo controlled trial from a few years ago asked this exact question. They compared treatment with local honey, a national brand, and placebo and found no difference in several allergy symptoms during a 6 month treatment period. So in the end, honey is exactly what it’s supposed to be: a sugar pill.
Dr. O
December 10th, 2008
Asthma is classified as an obstructive lung disease. This means asthmatics have difficulty getting air out or exhaling. This is caused by narrowing of the airways and manifests as wheezing or prolonged exhalation. The ability to move air in and out can be measured by a simple test called spirometry. Spirometry is an integral part of the management of asthma. It is such an important test, that everyone with asthma should do it at least once and most asthmatics need it more often.
The reason this is so important is twofold. First, there is a huge disconnect between how people perceive their asthma severity and the reality of their lung function. I commonly see people whose self-reported symptoms are minimal but whose lung function is poor. This makes a big difference in what medications to use. Second, listening to the lungs with a stethoscope, called auscultation (aw-skull-TAY-shun), cannot tell you all you need to know. Even if the lungs are clear, testing may reveal diminished lung function.
An important part of spirometry that is underutilized is called bronchodilator reversal. What this means is, after measuring the lung function, the patient is given a “breathing treatment” with albuterol and then the lung function is measured again. A significant change in lung function, or lack thereof, is a very important clue as to how active a person’s asthma is.
If you have asthma, and especially if you take regular asthma medications, you need to have your lung function measured to ensure that you are doing all you need to do to keep your asthma under control.
Dr. O
Post-post mini rant: A huge pet peeve of mine is calling spirometry “Pulmonary Function Testing” (PFT). Spirometry is one component of PFT, with the others being measurement of lung volumes and measurement of how well gas moves between the lungs and the bloodstream, called DLCO. Full PFTs are important in the diagnosis and management of many lung diseases, but asthma is not one of them.
December 4th, 2008
Who doesn’t like a good cupcake? For kids with food allergies, though, cupcakes can be a no-no. Fortunately for Nashville parents, two businesswomen have opened Kateelayne carefree treats, a bakery offering allergen-free cupcakes and cookies. They’re kosher and vegan,too. Check them out.
December 4th, 2008
“I love cats. They keep me in business.”- Anonymous allergist
Cat dander is probably the single most potent sensitizer of the airways. Felis domesticus, the common house cat, secretes a protein in its saliva and skin glands that is very tenacious in an indoor environment. Even with removal of a cat from a home, it can take months for cat dander levels to fall to normal background levels.
It’s not just homes with cats that are the problem, however. Cat dander is much more prevalent than most people realize. Studies have shown significant cat dander levels in subways, department stores, and even in brand new plastic-wrapped mattresses. Cat dander is the number one cause of asthma exacerbations at schools, where kids with cat sensitivity are forced into close proximity with kids toting large amounts of cat dander on their clothes.
So what can we do about cat dander? In my decade or so of practicing allergy, I can count on the fingers of one hand the number of people who got rid of their cat. And why would you? Pets are an integral part of many families, mine included. It’s the allergists job to fix the problem so you can live the life you want rather than requiring you to change your lifestyle to fit the problem!
Many people laugh at the idea of washing the cat regularly. Apparently cats have claws and many are not afraid to use them when confronted with water. Nevertheless, washing a cat with regualrity is the most effective method of reducing indoor cat dander levels. A HEPA filter in the bedroom can also reduce cat dander levels in the place where you spend the most time.
The reality is, though, that most cat-allergic cat owners wind up going on allergy shots to reduce their sensitivity. Even though the shots work less well when the cat remains in the home, they still are more effective than medications at reducing the sensitivity to cats.
Dr. O
December 3rd, 2008
The other day, a flier sent by a local chiropractor came across my office fax machine. Its 32-point tag line read, “Did you know that allergies are not caused by things in your environment, but by misalignment of the spine?” Actually, despite my 4 years of medical school, 3 years of residency, 3 years of fellowship, and 7 years of private practice, I was fully unaware of this! Apparently, this whole “immune system” scam has finally been debunked. I briefly considered walking the 4 doors down to his office to have him enlighten me, but I reasoned that most people who read that particular flier would see it for what it was: hogwash. I have nothing against chiropractors treating musculoskeletal problems- I see one myself from time to time- but this statement clearly showed either ignorance of or willing disregard for the truth.
This is but one example of numerous dubious practices relating to allergy. There are so many, in fact, that it would be impractical for me to list them all here. I’ll start with one that was highlighted in this week’s “Medical Letter”, an independent, non-profit publication that reviews drugs and medical devices. The reviewers examined low-voltage electronic diagnostic devices, which are essentially galvanometers- devices that measure resistance to electrical current. One such device, the Electroacupunctue According to Voll (EAV), requires the patient to hold a metal probe in one hand while the practitioner places a second probe on various “acupuncture points” on the patients other hand or foot. This completes an electrical circuit and the subsequent reading of current is said to reveal organ inflammation if the reading is high and “stagnation” if the reading is low. Certain “acupuncture points” are said to correspond to allergic inflammation. The Vegatest and Biomeridian are two devices which utilize EAV.
The FDA classifies low-voltage diagnostic devices as Class III, meaning they must have FDA approval prior to marketing. Since no EAV devices are FDA approved for diagnosing and managing disease, I’m not sure why they’re allowed to be used in the community. The Medical Letter reviewers summarize their look at these devices by saying, “Patients should be told that low-voltage electronic devices claimed to diagnose or treat a wide variety of health problems lack a scientifically plausible rationale and should be regarded as bogus.” I concur.
Dr. O
