More Americans may be allergic to sesame than previously believed, a new study finds.
Researchers from Northwestern University's Feinberg School of Medicine say as many as 1.5 million US children and adults have a sesame allergy, or about 0.5 percent of the US population.
That's five times higher than the number of Americans that was suggested in previous research.
However, sesame is not required by law to be included on ingredients labels like peanuts and dairy are, or is lumped under a generic term such as 'spices'.
A new study from Northwestern University's Feinberg School of Medicine found that half of children and one-third of adults with a sesame allergy were self-diagnosed (file image)
For the study, published in JAMA Network Open, the team surveyed around 50,000 US households, representing about 80,000 adults and children.
Participants were asked questions about suspected food allergies, actual diagnoses and allergic reactions.
Researchers found that up to 1.5 million Americans - or 0.49 percent of the population - could be allergic to sesame, with 1.1 million having an official diagnosis.
This may seem like a small number but previous studies, such as a 2010 study from Mount Sinai School of Medicine in New York, placed the prevalence of sesame allergies at 0.1 percent.
That's nearly five times lower than the new figures Northwestern present.
Of those with an allergy, researchers found that half of children and one-third of adults were self-diagnosed.
'Clinical confirmation of suspected food allergies is essential to reduce the risk of unnecessary allergen avoidance as well as ensure patients receive essential counseling and prescription of emergency epinephrine,' said first author Christopher Warren, an investigator with the Center for Food Allergy and Asthma Research.
Among those with a 'convincing allergy to sesame' - defined as experiencing at least one common symptom such as hives or wheezing - more than 62 percent said they'd been prescribed epinephrine.
Currently, eight allergens are required by the US Food and Drug Administration (FDA) to be listed on food labels: eggs, fish, milk, peanuts, shellfish, soy, tree nuts and wheat.
Sesame, however, is not required and can be listed on food labels under 'natural flavors' or 'spices' or not even at all.
Additionally, many people don't know that seeing 'tahini' on a food label, means sesame is one of the ingredients.
In the European Union, Canada, Australia and New Zealand, labeling for products that contain sesame is mandatory.
However, the FDA is considering requiring sesame to be listed on labels and, in October, issued a 'request for information, so we can learn more about the prevalence and severity of sesame allergies in the US'.
Just this week, Illinois became the first state requiring packaged food to include sesame on the ingredients label.
'Our study shows sesame allergy is prevalent in the US in both adults and children and can cause severe allergic reactions,' said lead author Dr Ruchi Gupta, a professor of pediatrics and medicine at the Feinberg School of Medicine.
'It is important to advocate for labeling sesame in packaged food. Sesame is in a lot of foods as hidden ingredients. It is very hard to avoid.'