The rate of hospital admissions in the United Kingdom for food-induced anaphylaxis more than tripled over the 20 years from 1998 to 2018, but the case fatality rate fell by more than half, researchers report in The BMJ.
“Cow’s milk is increasingly identified as the culprit allergen for fatal food reactions, and is now the commonest cause of fatal anaphylaxis in children,” write Alessia Baseggio Conrado, PhD, a biochemist with the National Heart and Lung Institute at Imperial College London, United Kingdom, and colleagues. “More education is needed to highlight the specific risks posed by cow’s milk to people who are allergic to increase awareness among food businesses.”
Whereas recognition of the risks posed by nut allergies has increased, people think milk allergy is mild, says senior author Paul. J. Turner, BM BCh, PhD, an allergist/immunologist at Imperial College. “This is often true in very young children, but school-aged children who still have milk allergy tend to have a more allergic profile, often with other allergies, including asthma,” Turner told Medscape Medical News. “Also, milk is very common in our diet, and you don’t need much milk to achieve a decent dose of allergen.”
During the study period, 101,891 people were hospitalized for anaphylaxis; 30,700 cases (30%) were coded as having been triggered by food.
These food-related admissions represent an increase from 1.23 to 4.04 per 100,000 population per year, for an annual increase of 5.7% (95% CI, 5.5 – 5.9; P < .001), the authors write.
The largest jump occurred among children younger than 15 years, for whom admissions rose from 2.1 to 9.2 per 100,000 population per year, an annual increase of 6.6% (95% CI, 6.3 – 7.0). The annual increases were 5.9% (95% CI, 5.6 – 6.2) among persons aged 15 to 59 years and 2.1% (95% CI, 1.8 – 3.1) among those aged 60 years and older.
The investigators used data from England, Scotland, Wales, and Northern Ireland to track temporal trends and age and sex distributions for hospital admissions for which the primary diagnosis was anaphylaxis due to both food and nonfood triggers. These data were compared with nationally reported fatalities.
Over the 20-year period, 152 deaths were attributed to likely food-induced anaphylaxis. During that time, the case fatality rate for confirmed fatal food anaphylaxis fell from .7% to .19% (rate ratio, 0.931; 95% CI, .904 – .959; P < .001) and declined to 0.30% for suspected fatal food anaphylaxis (rate ratio, .970; 95% CI, 945 – 0.996; P = .024).
Between 1992 and 2018, at least 46% of all anaphylactic fatalities were deemed to be triggered by peanut or tree nut. Among school-aged children, 26% of anaphylactic fatalities were attributed to cow’s milk.
Not surprisingly, during the study period, there was an increase of 336% in prescriptions for adrenaline autoinjectors. Such prescriptions increased 11% per year.
The data extend findings Turner and colleagues reported for England and Wales in 2014 regarding the entire UK population and align with epidemiologic trends in hospital admissions for anaphylaxis in the United States and Australia.
The researchers say better recognition and management of anaphylaxis could partly explain the decrease in fatalities, but the rise in hospitalizations remains puzzling. “Whether a true increase in the prevalence of anaphylaxis has occurred (rather than a reduction in the threshold to admit patients presenting with anaphylaxis) is unclear because evidence is lacking for an increase in prevalence of food allergy in the UK (and elsewhere) over the same time period,” they write.
Ronna L. Campbell, MD, PhD, an emergency physician at the Mayo Clinic in Rochester, Minnesota, has noted similar trends in the United States. “It may be that anaphylaxis recognition and diagnosis have improved, resulting in earlier administration of epinephrine,” Campbell told Medscape Medical News. “So while cases are increasing, earlier recognition and treatment result in decreased fatalities.” She is unaware of any new guidelines recommending increased hospitalization that would explain the puzzling rise in admissions.
According to the study authors, the clinical criteria used to diagnose anaphylaxis in the United Kingdom did not change during the study period. Although national guidance recommending the hospitalization of children younger than 16 who are suspected of having anaphylaxis was introduced in 2011 and may have boosted admissions, the year-on-year rate of increase has persisted since 2014. “Therefore the increase over the past five years cannot be attributed to the impact of the guidance,” they write.
The study was funded by grants from the UK Medical Research Council and UK Food Standards Agency. Two coauthors have disclosed financial relationships with industry outside of the submitted work. Conrado has disclosed no relevant financial relationships.
BMJ. Published online February 17, 2021. Full text
Diana Swift is a medical journalist based in Toronto.
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