Sesame allergy affects more than 1 million children and adults in the US, more than previously known, reports a new Northwestern Medicine study.

But sesame labeling is currently not required by law as are the other top eight allergens like peanut and milk, and is often labeled in a potentially confusing manner, such as tahini. This increases the risk of accidental ingestion.

The new study provides the first up-to-date estimates on the current prevalence of sesame allergy among US children and adults in all 50 states.

"Our study shows sesame allergy is prevalent in the US in both adults and children and can cause severe allergic reactions," said lead study author Dr. Ruchi Gupta, professor of pediatrics and of medicine at Northwestern University Feinberg School of Medicine and a physician at Ann & Robert H. Lurie Children's Hospital of Chicago. "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."

Gupta also is director of the Center for Food Allergy and Asthma Research at Feinberg.

The paper will be published August 2 in JAMA Network Open.

The study directly informs ongoing regulatory rule-making by the US Food & Drug Administration, which is currently considering whether sesame should be added to the list of key food allergens for which mandatory product labeling is required. Unlike in other countries (the European Union and Australia), current US law does not require sesame-containing products be labeled.

The Food Allergen Labeling and Consumer Protection Act of 2014 mandates labeling of the top eight allergenic foods/food groups including peanut, milk, shellfish, tree nuts, egg, wheat, soy and finfish along with proteins derived from them.

More than 1.5 million children and adults in the US (.49% of the population) report a current sesame allergy, and more than 1.1 million (.34% of the population) report either a physician-diagnosed sesame allergy or a history of sesame-allergic reaction symptoms, the study found.

The data also indicate many individuals who report sesame allergies and experience potentially severe allergic reactions are not obtaining clinical diagnosis of their allergies.

"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.

Unlike allergies such as milk or egg, which often develop early in life and are outgrown by adolescence, sesame allergy affects children and adults to a similar degree. In addition, four in five patients with sesame allergy have at least one other food allergy. More than half have a peanut allergy, a third are tree-nut allergic, a quarter are egg-allergic and one in five are allergic to cow's milk.

Study investigators administered a survey via telephone and web to more than 50,000 US households. The survey asked detailed information about any suspected food allergies, including specific allergic reaction symptoms, details about clinical diagnosis of food allergies as well as demographic information. They obtained responses for a nationally representative sample of approximately 80,000 children and adults.