Surprisingly common in older people, food allergies can interfere with adequate nutritional intake, according to an Italian systematic review and meta-analysis published in the World Allergy Organization Journal.

With the global rise in food allergies, research has largely focused on younger groups, yet older adults have distinct risk factors such as immunosenescence, chronic inflammation, micronutrient deficiencies, multimorbidity, and polypharmacy, which could influence allergic responses, wrote study investigators led by Domenico Azzolino, PhD, nutritional scientist in the Geriatric Unit of the Ospedale Maggiore Policlinico in Milan, Italy.

In fact, food-induced anaphylaxis has been reported to account for 6% of emergency department visits and 4.1% of hospitalizations among Americans aged 65 years or older.

Because food allergies reflect a loss of tolerance to specific food proteins, their management relies primarily on allergen avoidance. “Inadequate consumption of protein-rich foods such as meat, milk, eggs, and fish is common in older adults and, when compounded by allergen avoidance, may create a vicious cycle of further protein restriction and increased risk of undernutrition and functional decline,” Azzolino and colleagues wrote.

The Study

With data on food allergies in this age group very sparse, the researchers examined prevalence in 16 studies published from 2004 to 2023 conducted in Europe, North and South America, the Middle East, and Asia. Most were graded as having a moderate risk for bias.

The pooled prevalence of self-reported food allergies was 12% (95% CI, 9%-15%). Self-reported physician-diagnosed food allergies had a prevalence of 7% (95% CI, 5%-8%). Specific immunoglobulin E (sIgE) sensitization indicated a prevalence of 14% (95% CI, 10%-18%), with sIgE sensitization to common allergens at 3% for cow’s milk and peanut, 2% for egg, and 1% for soy.

Exploratory comparisons tentatively suggested similar combined prevalence estimates across low- and middle-income countries (10%) and high-income countries (9%).

The prevalence of any type of food allergy varied by setting, country, and assessment method, with a range from 1% to 25%.

The prevalence of clinically confirmed food allergy remains poorly defined, the authors cautioned. “The limited evidence and heterogeneity across studies highlight the need for standardized diagnostic criteria and greater inclusion of older adults in future food allergy research.”

The investigators also called for physicians and older persons to avoid normalizing food allergy symptoms as part of the aging process. The identification of food allergies in older adults should be part of routine clinical practice to avoid both anaphylactic reactions and adverse consequences for nutritional status, said Azzolino and associates.

Offering a US perspective, David B. Corry, MD, professor of immunology, allergy, and rheumatology at Baylor College of Medicine in Houston, said he and his colleagues are seeing more consultations for food allergies among adults of all ages now at the Michael E. DeBakey VA Medical Center compared with 10 or 15 years ago when these consultations were rare. “My experience is that food allergies are quite uncommon in the over-60 age group but still markedly higher now,” said Corry, who was not involved in the meta-analysis.

In his view, front-line physicians are not usually sufficiently aware of the need to identify food allergies. “Some do screen adequately for this, but most do not.”

Corry cautioned that the findings remain uncertain because high-quality confirmatory data on the existence of food allergies were lacking in most of the papers available to the research team.

Ruchi Gupta, MD, MPH, professor of pediatrics and medicine and director of the Center for Food Allergy & Asthma Research at Northwestern Feinberg School of Medicine in Chicago, offered another US viewpoint on the study but was not involved in the research. She stressed that food allergies are a lifelong burden, not just a pediatric condition, and de novo adult-onset food allergies are well documented. “Half of adults reporting convincing allergies report developing a new allergy as an adult,” she told Medscape Medical News.

The progressive remodeling of the older immune system can result in secondary sensitization, she explained. “The most common form of adult-onset food allergy is pollen-food allergy syndrome, or oral allergy syndrome, driven by cross-reactivity between environmental pollens and structurally similar plant food proteins.”

Age-related delayed gastric emptying and the widespread use of proton pump inhibitors can impair proper protein digestion. “This allows intact, conformationally stable food proteins to pass through the intestinal mucosa, potentially eliciting new IgE production. We are also learning more about how environmental and microbiome changes impact the immune system,” she added.

Her center is investigating how aging affects the immune system’s tolerance to food because older cohorts represent one of the fastest-growing yet least-understood demographics in allergy research. Under development is a validated tool for assessing food allergy to help align the prevalence numbers across the globe.

In her view, best practice should rely on targeted, proactive clinical history taking. “If a patient describes symptoms consistently correlating with specific food ingestion, a careful, customized diagnostic workup should be initiated.” If an allergy is confirmed and an elimination diet is required, she said, an immediate referral to a dietitian is essential to ensure adequate protein and micronutrient intake to prevent frailty.

This research was partially funded by the Italian Ministry of Health. The authors and commentator Corry declared no conflicts of interest. Gupta reported research support from the National Institutes of Health, Food Allergy Research & Education, Sunshine Charitable Foundation, Genentech, Novartis, and Abbott Laboratories. She serves as a medical consultant/adviser to Genentech, DBV Technologies, Simply Good, Kaléo, Bryn Pharma, and ARS Pharmaceuticals. She has an ownership interest in Yobee Care, Inc. and is currently employed by Ann & Robert H. Lurie Children’s Hospital of Chicago.