NIH Researchers Estimate 17% of Food-Allergic Children Have Sesame Allergy

Investigators at the National Institutes of Health have found that sesame allergy is common among children with other food allergies, occurring in an estimated 17% of this population.

Sesame seeds. NIAID

In addition, the scientists have found that sesame antibody testing — whose utility has been controversial — accurately predicts whether a child with food allergy is allergic to sesame. The research was published on Oct. 28 in the journal Pediatric Allergy and Immunology.

“It has been a challenge for clinicians and parents to determine if a child is truly allergic to sesame,” said Anthony S. Fauci, M.D., director of the National Institute of Allergy and Infectious Diseases (NIAID), part of NIH. “Given how frequently sesame allergy occurs among children who are allergic to other foods, it is important to use caution to the extent possible when exposing these children to sesame.”

Sesame is among the 10 most common childhood food allergies. Only an estimated 20% to 30% of children with sesame allergy outgrow it. Severe reactions to sesame are common among sesame-allergic children. About 1.1 million people in the United States, or an estimated 0.23% of the U.S. population, have sesame allergy, according to a recently published study funded by NIAID. These factors underscore the need to optimize recognition and diagnosis of this allergy. The Food and Drug Administration is currently considering whether to include sesame in the list of allergens that must be disclosed on food labels.

Standard allergy tests — the skin-prick test and the allergen-specific antibody test — have been inconsistent in predicting an allergic reaction to sesame. Many studies evaluating the utility of these tests for sesame allergy have included only children suspected to have sesame allergy. Taking a different approach, scientists led by Pamela A. Frischmeyer-Guerrerio, M.D., Ph.D., deputy chief of the NIAID Laboratory of Allergic Diseases and chief of its Food Allergy Research Unit, evaluated the sesame antibody test in a group of 119 children with food allergy whose sesame-allergic status was unknown.

The researchers offered children in the study an oral food challenge — the gold standard for diagnosing food allergy — which involved ingesting gradually increasing amounts of sesame under medical supervision and seeing if an allergic reaction occurred. Children who recently had had an allergic reaction to sesame or were known to tolerate concentrated sesame, such as tahini, in their diet were not offered an oral food challenge.

The scientists found that 15 (13%) of the 119 children were sesame-allergic, 73 (61%) were sesame-tolerant, and sesame-allergic status could not be determined for 31 (26%) children, mainly because they declined the oral food challenge. Among the 88 children whose sesame-allergic status was definitive, 17% had sesame allergy.

The scientists measured the amount of an antibody called sesame-specific immunoglobulin E (sIgE) in the blood of these 88 children. With this data and information on the children’s sesame-allergic status, the researchers developed a mathematical model for predicting the probability that a child with food allergy is allergic to sesame. According to the model, children with more than 29.4 kilo international units of sIgE per liter of serum have a greater than 50% chance of being allergic to sesame. This model will need to be validated by additional studies, however, before it can be used in clinical practice.   

Scientists Identify Unique Subtype of Eczema Linked to Food Allergy

Children with Both Conditions have Abnormal Skin Near Eczema Lesions, NIH-Funded Research Finds

A researcher demonstrates the minimally invasive collection of skin samples using small, clear tape strips.
Credit: National Jewish Health

Atopic dermatitis, a common inflammatory skin condition also known as allergic eczema, affects nearly 20 percent of children, 30 percent of whom develop food allergies.

Scientists have now found that children with both atopic dermatitis and food allergy have structural and molecular differences in the top layers of healthy-looking skin near the eczema lesions, whereas children with atopic dermatitis alone do not.

Defining these differences may help identify children at elevated risk for developing food allergies, according to research published online today in Science Translational Medicine. The research was supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health. 

“Children and families affected by food allergies must constantly guard against an accidental exposure to foods that could cause life-threatening allergic reactions,” said NIAID Director Anthony S. Fauci, M.D. “Eczema is a risk factor for developing food allergies, and thus early intervention to protect the skin may be one key to preventing food allergy.” Children with atopic dermatitis develop patches of dry, itchy, scaly skin caused by allergic inflammation.  Atopic dermatitis symptoms range from minor itchiness to extreme discomfort that can disrupt a child’s sleep and can lead to recurrent infections in scratched, broken skin.

A drawing of skin and a hair follicle. In this study, scientists analyzed the outermost layer of the skin, the stratum cornea, highlighted here in yellow.Credit: NIAMS, NIH

The study, led by Donald Y.M. Leung, M.D., Ph.D., of National Jewish Health in Denver, examined the top layers of the skin, known as the stratum corneum, in areas with eczema lesions and in adjacent normal-looking skin. The study enrolled 62 children aged 4 to 17 who either had atopic dermatitis and peanut allergy, atopic dermatitis and no evidence of any food allergy, or neither condition. Investigators collected skin samples by applying and removing small, sterile strips of tape to the same area of skin. With each removal, a microscopic sublayer of the first layer of skin tissue was collected and preserved for analysis. This technique allowed researchers to determine the skin’s composition of cells, proteins and fats, as well as its microbial communities, gene expression within skin cells and water loss through the skin barrier.

Researchers found that the skin rash of children with both atopic dermatitis and food allergy was indistinguishable from the skin rash of children with atopic dermatitis alone. However, they found significant differences in the structure and molecular composition of the top layer of non-lesional, healthy-appearing skin between children with atopic dermatitis and food allergy compared with children with atopic dermatitis alone. Non-lesional skin from children with atopic dermatitis and food allergy was more prone to water loss, had an abundance of the bacteria Staphylococcus aureus, and had gene expression typical of an immature skin barrier. These abnormalities also were seen in skin with active atopic dermatitis lesions, suggesting that skin abnormalities extend beyond the visible lesions in children with atopic dermatitis and food allergy but not in those with atopic dermatitis alone.

“Our team sought to understand how healthy-looking skin might be different in children who develop both atopic dermatitis and food allergy compared to children with atopic dermatitis alone,” said Dr. Leung. “Interestingly, we found those differences not within the skin rash but in samples of seemingly unaffected skin inches away. These insights may help us not only better understand atopic dermatitis, but also identify children most at risk for developing food allergies before they develop overt skin rash and, eventually, fine tune prevention strategies so fewer children are affected.”

Allergy experts consider atopic dermatitis to be an early step in the so-called “atopic march,” a common clinical progression found in some children in which atopic dermatitis progresses to food allergies and, sometimes, to respiratory allergies and allergic asthma. Many immunologists hypothesize that food allergens may reach immune cells more easily through a dysfunctional skin barrier affected by atopic dermatitis, thereby setting off biological processes that result in food allergies. 

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Reference:  D Leung et al. Non-lesional skin surface distinguishes atopic dermatitis with food allergy as unique endotype. Science Translational Medicine DOI: 10.1126/scitranslmed.aav2685 (2019).