WEBVTT - Why Do People Get Adult-Onset Food Allergies? 0:00:02.040 --> 0:00:06.880 Welcome to brain Stuff from How Stuff Works High Brain 0:00:06.960 --> 0:00:09.800 Stuff Lauren Vogel bomb Here, we often think of food 0:00:09.840 --> 0:00:12.920 allergies as kids stuff. You know, a peanut free elementary 0:00:12.920 --> 0:00:15.760 school classrooms, a special carton of dairy free ice cream 0:00:15.800 --> 0:00:18.320 at birthday parties, and that one friend who couldn't eat 0:00:18.400 --> 0:00:21.520 anything containing red food die, which meant you got all 0:00:21.560 --> 0:00:24.840 their primo Halloween candy. But we don't always develop our 0:00:24.880 --> 0:00:27.920 allergies as children. It's just that childhood food allergies are 0:00:27.960 --> 0:00:31.280 studied more often than those acquired in adulthood. However, new 0:00:31.280 --> 0:00:34.000 research presented at the annual meeting of the American College 0:00:34.040 --> 0:00:38.000 of Allergy, Asthma and Immunology found that of all American 0:00:38.040 --> 0:00:41.000 adults with food allergies have at least one allergy that 0:00:41.120 --> 0:00:46.280 only materialized in adulthood. In the Chicago based research team 0:00:46.320 --> 0:00:49.000 found that at least fifteen percent of adult food allergy 0:00:49.040 --> 0:00:52.319 patients receiving care at Northwestern Medicine had at least one 0:00:52.360 --> 0:00:55.880 adult onset food allergy. However, this was a small, non 0:00:55.920 --> 0:00:59.680 representative sample of just Chicago area adults for this new study, 0:00:59.760 --> 0:01:02.279 these of it a nationally representative sample of more than 0:01:02.360 --> 0:01:05.759 fifty thousand adults, allowing the researchers to draw conclusions about 0:01:05.800 --> 0:01:09.399 the national prevalence of adult onset food allergies, and it's 0:01:09.400 --> 0:01:12.800 a lot higher than anyone anticipated given studies from previous decades. 0:01:13.200 --> 0:01:15.520 The research team notes that while a two thousand four 0:01:15.560 --> 0:01:18.520 study estimated that two point five percent of adult Americans 0:01:18.520 --> 0:01:21.440 were allergic to shellfish, the most common food allergy among 0:01:21.480 --> 0:01:24.600 adults in the United States, this twenty seventeen study found 0:01:24.640 --> 0:01:27.080 that number is more like three point six percent of 0:01:27.080 --> 0:01:30.200 the population. The same goes with tree nut allergies. A 0:01:30.280 --> 0:01:32.920 two thousand eight study estimated that only zero point five 0:01:32.920 --> 0:01:35.560 percent of American adults were allergic, but this new data 0:01:35.600 --> 0:01:38.760 saw a two hundred and sixty percent increase, with an 0:01:38.840 --> 0:01:41.520 estimated one point eight percent of adults having to avoid 0:01:41.720 --> 0:01:45.520 everything from ntella to Reese's peanut buttercups. We spoke with 0:01:45.560 --> 0:01:47.880 one of the studies co authors, Christopher Warren, whose a 0:01:47.960 --> 0:01:51.640 doctoral candidate in preventative medicine at the University of Southern California, 0:01:51.720 --> 0:01:55.880 via email. He said adult onset allergies are particularly interesting 0:01:55.920 --> 0:01:58.960 to study because they likely involve losing immune tolerance to 0:01:59.040 --> 0:02:02.200 foods that adults have already been previously exposed to and 0:02:02.320 --> 0:02:05.600 eaten without having an allergic reaction. This is in contrast 0:02:05.680 --> 0:02:08.680 to childhood food allergies, which involve the immune system failing 0:02:08.680 --> 0:02:11.359 to develop tolerance to these allergic foods in the first place. 0:02:11.840 --> 0:02:15.600 There may be two distinct mechanisms at work here. So 0:02:15.840 --> 0:02:18.320 why would adults be losing their immunity chops when it 0:02:18.360 --> 0:02:21.280 comes to certain foods. A possible clue might lie in 0:02:21.320 --> 0:02:24.519 the demographic trends found in the study. The research team 0:02:24.520 --> 0:02:27.320 found that certain populations were more at risk for specific 0:02:27.360 --> 0:02:31.080 adult onset food allergies than others. For instance, Hispanic adults 0:02:31.080 --> 0:02:33.400 were more than twice as likely to develop allergies to 0:02:33.400 --> 0:02:36.040 peanuts than whites, and Asians were more than twice as 0:02:36.040 --> 0:02:39.840 likely to develop shellfish allergies than whites. Warren said that 0:02:39.840 --> 0:02:42.239 there are a number of hypotheses for why this may be. 0:02:42.840 --> 0:02:45.280 For example, the cultural differences in the way that people 0:02:45.320 --> 0:02:49.280 of different backgrounds prepare allergenic foods could possibly influence the 0:02:49.360 --> 0:02:52.400 rates of allergies to those foods. According to Warren, when 0:02:52.440 --> 0:02:54.680 foods like peanuts are roasted in the presence of sugar, 0:02:54.840 --> 0:02:58.400 undergoing a browning process known as the Millard reaction, compounds 0:02:58.440 --> 0:03:02.359 called advanced glycati and end products are created. These compounds 0:03:02.360 --> 0:03:06.360 have been shown to increase the allergenicity of foods. Boiling foods, 0:03:06.400 --> 0:03:09.040 on the other hand, tends to make their proteins less allergenic. 0:03:09.360 --> 0:03:12.160 This hypothesis may explain the low rates of peanut allergy 0:03:12.200 --> 0:03:15.639 in Asia, where peanuts are typically boiled or fried, relative 0:03:15.680 --> 0:03:18.760 to the Americas, where peanuts are typically dry roasted. This 0:03:18.880 --> 0:03:21.400 is consistent with what the current research team found out 0:03:21.440 --> 0:03:24.839 about the prevalence of seafood allergies among Asian American participants. 0:03:25.200 --> 0:03:27.960 Other population based studies conducted in Asia have found that 0:03:28.000 --> 0:03:31.280 shellfish allergies are the most common allergy among older children 0:03:31.320 --> 0:03:35.040 and adults there as well. However, diet might not have 0:03:35.120 --> 0:03:38.040 everything to do with why certain populations develop allergies to 0:03:38.080 --> 0:03:41.520 specific foods with higher frequency. Warren told us about an 0:03:41.520 --> 0:03:44.640 ongoing study into the allergies of over five thousand children 0:03:44.640 --> 0:03:47.920 that's being conducted in Australia called health Nuts. He said 0:03:48.200 --> 0:03:50.120 a recent work out of the Health Nuts cohort in 0:03:50.120 --> 0:03:53.920 Australia suggests that the Asian environment may be protective against 0:03:53.960 --> 0:03:57.120 food allergy. Australian born Asian children are at a much 0:03:57.200 --> 0:03:59.960 higher risk of developing food allergies than Asian born kids. 0:04:00.000 --> 0:04:03.080 It's who moved to Australia, possibly because they've been exposed 0:04:03.120 --> 0:04:07.160 to a different diet, bacterial, and uv environment. Warren and 0:04:07.240 --> 0:04:09.560 his co authors are interested in looking at differences in 0:04:09.600 --> 0:04:12.120 food allergy prevalence in the United States to see if 0:04:12.120 --> 0:04:15.560 similar differences are observable among US immigrants relative to those 0:04:15.600 --> 0:04:18.080 born in the States. We'll be on the lookout for updates. 0:04:23.440 --> 0:04:26.320 Today's episode was written by Jesslyn Shields and produced by 0:04:26.360 --> 0:04:28.680 Tristan McNeil. For more on this and lots of other 0:04:28.720 --> 0:04:43.640 health topics, visit our home planet, how Stuff Works dot com.