Evaluation prompted by other food allergies may reveal latent sesame allergy
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PHOENIX — Many sesame-allergic patients only underwent testing for sesame allergy after having been diagnosed with other food allergies, with just one-third of patients having had a prior reaction to sesame, according to study results.
Results of this study — the largest retrospective study of sesame-allergic patients, which was presented at the American Academy of Allergy, Asthma & Immunology Annual Meeting — also showed that sesame allergy was less likely to resolve among patients with concomitant peanut and tree nut allergies.
“Sesame allergy is a growing concern in the U.S. and elsewhere and its prevalence is on the rise,” Rima Rachid, MD, director of the Allergen Immunotherapy Program and co-director of the Food Allergy Program at Boston Children's Hospital, told Healio.
Rachid cited data from a 2010 cross sectional study that estimated the prevalence of sesame allergy to be 0.1%, whereas a 2019 cross-sectional study showed a 0.49% rate of self-reported sesame allergy among U.S. adults and children.
“Sesame is now recognized by the FDA as the ninth common food allergen in the United States,” she added. “The FDA recently mandated labeling of sesame as an allergen on food products effective January 2023. However, little is known about sesame allergy presentation natural history and outcomes.”
To further characterize sesame allergy and understand its presentation and outcomes, Rachid and colleagues searched the i2b2 dataset to identify all sesame-allergic patients who were evaluated at the Boston Children’s Hospital allergy program.
The analysis included 1,394 patients (38.1% female), who were diagnosed with sesame allergy at a mean age of 4.2 years.
Mean follow-up was 4 years (range, 0-20.5).
More than half of the patients (53%) underwent sesame testing due to having another food allergy, and 94% of patients had a concomitant tree nut or peanut allergy.
“Previous studies have demonstrated a serological or clinical cross-reactivity between peanut, tree nut and sesame allergy,” lead study author Farida Abi Farraj, MD, postdoctoral research fellow at Boston Children’s Hospital, told Healio. “Other studies also demonstrated cross-reacting allergens between sesame and tree nut or sesame and peanut, which could explain why these allergies are co-occurring.
“We also think that there is likely increase testing for sesame allergy when patients present with peanut and/or tree nut allergies,” she added.
Further, only 37.2% of patients had experienced at least one prior confirmed allergic reaction to sesame, with 9.8% having experienced anaphylaxis.
Researchers also found that patients also commonly had allergic rhinitis (67%) and eczema (73%).
Only 8.4% of patients had documented resolution of their sesame allergy, with resolution less likely to occur among those with an ongoing history of peanut or tree nut allergy (P < .001 for both) or who had a history of sesame reactions (P = .035).
Patients with a sesame skin prick test with an 8 mm wheal or larger were more likely to have a history of allergic reactions or anaphylaxis to sesame (P < .001 for both) and eczema (P = .016).
Also, sesame IgE of 10 kU/L or greater appeared linked to use of epinephrine (P = .022), emergency visits (P = .031), allergic rhinitis (P = .006), eczema (P = .001) and asthma (P = .013).
“Larger and longer longitudinal studies are needed to evaluate the natural rate of resolution of sesame allergy and also to further evaluate the 50% and 95% positive-predictive values of sesame-specific skin test wheal size and serum IgE level for failing a sesame food challenge,” Rachid said.
Also, more study is needed to explore the fact that a high number of patients with sesame allergy had concomitant peanut and tree nut allergies without having a prior sesame reaction, Abi Farraj said.
“It is unclear how many of these patients are sensitized without clinical reactivity (ie, they have a false-positive result, are falsely diagnosed and would not react when given sesame) and how many are truly allergic,” she said. “It is critical to evaluate these patients further by performing food challenges, especially when their sesame skin test wheal results are not too large and/or their serum sesame IgE is not too elevated.
“A low number of patients undergo a food challenge, which implies that further discussion with patients and their families is warranted about the possibility of doing food challenges and identification of reasons for not doing them,” she added.
References:
- Beyer K, et al. J Allergy Clin Immunol. 2002;doi:10.1067/mai.2002.125487.
- Dubiela P, et al. Sci Rep. 2018;doi:10.1038/s41598-018-29656-4.
- Sicherer SH, et al. J Allergy Clin Immunol. 2010;doi:10.1016/j.jaci.2010.03.029.
- Tuano KT, et al. Ann Allergy Asthma Immunol. 2016;doi:10.1016/j.anai.2016.09.003.
- Warren CM, et al. JAMA Netw Open. 2019;doi:10.1001/jamanetworkopen.2019.9144.
Perspective
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Broadly speaking, these data are remarkably consistent with survey findings from a large, nationally representative sample of U.S. households our group at the Northwestern University Center for Food Allergy and Asthma Research conducted a few years ago. Our survey data also showed high rates of comorbid atopy, including peanut and tree nut allergies, comparable (albeit slightly higher) rates of anaphylaxis and low rates of sesame allergy resolution.
The only big surprise in the findings was the fact that there was such a relative preponderance of girls with sesame allergy, compared with boys, given that in general there is a male skew in pediatric food allergy, and our survey data suggested that this was also the case for pediatric sesame allergy.
There is some evidence that the prevalence of sesame allergy has increased. In a 2008 national survey of 13,534 individuals conducted by Sicherer and colleagues, the self-reported prevalence of sesame allergy was estimated at 0.1%, whereas a more recent survey by our group found that roughly 0.5% had a reported allergy but, of these, fewer than half were likely to have a true IgE-mediated allergy. This does suggest that the prevalence is increasing, at least in the U.S.
However, at least some of this apparent increase in prevalence is likely a result of greater awareness of sesame allergy and food allergies in general due to the success of food allergy patient advocacy efforts and ongoing efforts to expand federal labeling laws to include sesame. These efforts recently culminated in the passage of the FASTER Act of 2021, which expanded the definition of major food allergen for purposes of certain food-labeling requirements to specifically include sesame.
Many questions remain on sesame allergy. One key question is how many sesame-allergic individuals in the U.S. are having serious allergic reactions to sesame due to accidental consumption of unlabeled sesame products vs. consumption of labeled sesame products vs. intentional consumption.
Another is how to accurately predict the eliciting dose of sesame for a given patient so that useful guidance can be provided regarding how worried a patient needs to be regarding risk associated with consuming small quantities of sesame seed (eg, cross-contact or a few sesame seeds on a bun, or sprinkled atop a dish).
Finally, given the extent to which hummus and tahini are increasingly being consumed in the U.S., can early introduction of sesame-containing foods such as tahini prevent sesame allergy in high-risk infants? And if so, what is the minimum necessary dose, frequency and optimal timing to maximize this protective effect for a given patient?
References:
Sicherer SH, et al. J Clin Allergy Immunol. 2010;doi:10.1016/j.jaci.2010.03.029.
Warren CM, et al. JAMA Netw Open. 2019;doi:10.1001/jamanetworkopen.2019.9144.
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Abi Farraj F, et al. Abstract L17. Presented at: AAAAI Annual Meeting; Feb. 25-28, 2022; Phoenix (hybrid meeting).
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