Seafood

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Clinical Rounds

SKIN & ALLERGY NEWS • April 2007

Myth Persists on Seafood Allergy/Contrast Link BY ROBERT FINN

San Francisco Bureau

S A N D I E G O — An old medical myth— that patients who are allergic to seafood are at risk of adverse reactions to radiologic contrast media—persists even among cardiologists and interventional radiologists, despite having been thoroughly debunked, Dr. Andrew D. Beaty reported at the annual meeting of the American Academy of Allergy, Asthma, and Immunology. In a survey of 231 specialists at six academic medical centers, 69% of physicians admitted asking patients about seafood allergy before radiologic procedures using contrast media. Of those surveyed, 37% of physicians admitted withholding contrast media or premedicating seafood-allergic patients with corticosteroids or antihistamines before the procedure. Many studies over the past 30 years have failed to find any special relationship between seafood allergy and adverse reactions to radiologic contrast media (RCM). According to some small studies, atopic patients in general may have a fourfold to fivefold increased risk of adverse events in response to RCM. However, the baseline rate of these events is so low that even if confirmed in larger populations, less than 1% of atopic patients would be affected.

About 10 million procedures using Furthermore, IgE does not mediate severe RCM are conducted every year in the RCM reactions. The combination of these United States. Life-threatening reactions two findings effectively discounts the hyoccur in about 0.2% of patients receiving pothesis of iodine cross-reactivity. For his study, Dr. Beaty and his colhigh-osmolarity contrast media and 0.04% of patients receiving low-osmo- leagues mailed anonymous questionnaires to 231 faculty members at six larity contrast media. The origin of the seafood-allergy myth prominent academic medical centers in is unknown. But Dr. Beaty, of St. Louis the Midwest. Of the individuals queried, 49% responded. University, has traced The survey consistit at least as far as a Many studies over the past ed of eight brief 1975 paper in the 30 years have failed to find questions, but only American Journal of two of them related Roentgenology that any special relationship to seafood allergy stated that 15% of between seafood allergy and RCM. The other patients who experisix were intended as enced adverse reacand adverse reactions to distractors. tions to RCM reportradiologic contrast media. The first seafooded having seafood related question was, allergy (Am. J. Roentgenol. Radium Ther. Nucl. Med. “Do you or someone on your behalf in1975;124:145-52). The authors of that quire about a history of seafood or shellstudy hypothesized that the iodine in fish allergy prior to administration of conseafood cross-reacted with the iodine in trast media?” Sixty-five percent of the RCM. They never verified those patient re- radiologists and 89% of the cardiologists ports, however, and similar percentages of answered, “Yes.” The second question was, “Would you patients with adverse reactions in their study reported allergies to other common withhold RCM administration or recommend pretreatment with corticosteroids foods such as milk and eggs. Since then, it has been determined that and/or antihistamines based on a history seafood allergy is mediated by im- of seafood or shellfish allergy?” Thirty-five munoglobulin E (IgE) antibodies to pro- percent of the radiologists and 50% of the teins in meat, with iodine playing no role. cardiologists answered, “Yes.”

While 69% of the total respondents said that they would ask patients about seafood allergy, only 37% said that they would change management based on that information. That suggests that about 32% would ask the question even if the answer would not affect patient management. Merely asking that question may serve to perpetuate the myth among patients, Dr. Beaty said. He pointed to a separate study indicating that 65% of patients with seafood allergy had either read or been told by their physician to avoid RCM, and 92% believed that iodine in seafood was responsible for their allergy (Allergy Asthma Proc. 2005;26:468-9). One audience member described a radiologic technician who received an official reprimand for failing to ask a patient about seafood allergy. Another said that at his institution no allergic patients were allowed to receive RCM unless they were premedicated. A third physician said that at his institution, the computer system automatically categorized every patient with a seafood allergy as being sensitive to RCM, and every patient who was sensitive to RCM as having a seafood allergy. That has now been changed, but patients who were seen before the change will have that erroneous information persist in their records until someone changes it manually. ■

One-Third of Egg-Allergic Some Consumers Are Ignoring Cautionary Food Allergen Labels Children Are Tolerant by Age 5 BY DOUG BRUNK

San Diego Bureau

S A N D I E G O — Since the Food Allergen Labeling and Consumer Protection Act of 2004 took effect last year, 64% of consumers who must avoid food allergens have noticed major allergens added to ingredient lists. Yet 25% are likely to buy products that contain precautionary allergen statements, such as “manufactured in a facility that also processes milk” or “packaged in a facility that also packages peanuts or other nuts.” The finding is important because there has been no formal assessment of consumer response to the labeling act, which mandates that food manufacturers disclose major allergens on lists of ingredients but does not establish standards for advisory statements like “may contain,” Dr. Scott H. Sicherer said at the annual meeting of the American Academy of Allergy, Asthma, and Immunology. In a study led by his associate, Dr. Heather Lemon-Mule, the researchers surveyed 645 parents of children with food allergies and others who attended 2006 Food Allergy and Anaphylaxis Network meetings in New York, Baltimore, and Chicago. The majority of respondents were parents of children with food allergies, said Dr. Sicherer, of the department of pediatrics at Mount Sinai School of Medicine, New York. More than half of respondents (64%) reported noticing that major food allergens have been added to ingredient lists, whereas 18% were unaware of such changes. The al-

lergen they noticed most often on ingredient lists was milk (61%), followed by peanuts (55%), tree nuts (38%), egg (31%), wheat (21%), soy (21%), and “other” (6%). More than one-fourth of respondents (28%) contacted manufacturers to ask about allergens added to ingredient lists. Yet in 46% of cases, manufacturers told them that the allergen was a newly added ingredient. At the same time, 83% of survey respondents reported noticing that new precautionary labels about allergens like “may contain milk or milk products” began to appear on products. The allergen they noticed most often on labels was peanuts (84%), followed by tree nuts (67%), milk (59%), egg (45%), wheat (35%), soy (35%), and “other” (14%). Overall, 20% reported contacting food manufacturers to ask about precautionary labels, yet only 14% of manufacturers said that the addition of such labels were directly related to product formula changes. Of respondents, 75% said they would never purchase a product with a precautionary label specific to their food allergy. However, wording appears to affect behavior. For example, about 91% would not buy products with the words “may contain” or “may contain traces of ” on the label. That response fell to 85% for statements like “manufactured with the same equipment as,” to 70% for labels with “manufactured in a facility that also processes,” and to 65% for statements such as “packaged in a facility that also packages.” He acknowledged a limitation of the study was its reliance on self-reported data. ■

BY DOUG BRUNK

San Diego Bureau

S A N D I E G O — About one-third of egg-allergic children develop tolerance by age 5 years and another onethird develop tolerance by age 10, Dr. Ralf G. Heine reported at the annual meeting of the American Academy of Allergy, Asthma, and Immunology. The finding is important because while egg-allergic children are believed to develop tolerance by school age, “there are few hard data on this,” said Dr. Heine, an allergist and gastroenterologist with Royal Children’s Hospital in Melbourne. “We know that a small number of people will develop persistent egg allergy. Due to the lack of [research] effort in this area we have to define the clinical manifestations and natural history of egg allergy presenting in children.” He and his associates reviewed the charts of 141 boys and 77 girls aged 2 years and younger who were evaluated for egg allergy in 1996 and had a skin prick test wheal diameter of 5 mm or greater. The researchers then compared the clinical parameters of children who developed egg tolerance by 5 years of age to those who had persistent egg allergy. The median follow-up period was 37 months and the researchers used a skin prick test wheal diameter of 7 mm or

greater for follow-up tests on children older than 2 years of age. Dr. Heine reported that of 218 children, 105 (48%) were diagnosed after a clinical reaction to egg, while the remaining 113 (52%) were diagnosed after a positive skin prick test. The most common clinical presentation was atopic dermatitis, which occurred in 179 of the children (82%). Common clinical symptoms on first known exposure included urticaria (26%), angioedema (12%), vomiting (11%), and nonurticarial rashes (7%). By the time children were 5 years of age, 33% developed tolerance to uncooked egg while another 34% developed egg tolerance by 10 years of age. The researchers observed that children in the persistent egg allergy group had a greater skin prick test wheal diameter, a higher level of eggspecific IgE, and a higher total serum IgE at diagnosis compared with their counterparts in the egg-tolerant group. They were also more likely to be male. Other factors associated with a high risk of developing persistent egg allergy were concomitant allergy to peanuts, tree nuts, and rye grass. The percentage of children with atopic dermatitis on follow-up was lower in the egg-tolerant group compared with the persistent egg allergy group (76% vs. 89%, respectively). ■