Older adults are at greater risk for severe anaphylaxis in a variety of settings but are less likely to receive epinephrine than younger adults, two recent studies have found.

In the first study, published last month in JACI in Practice, investigators determined that older adults had increased odds of reactions to medications and intravenous (IV) contrast and of experiencing cardiovascular symptoms than younger adults with anaphylaxis.

Cardiovascular Concerns or Anaphylaxis?

“Recognition of anaphylaxis is more difficult in older adults because they are less likely to show typical skin findings like hives or throat tightness, and more likely to present with cardiovascular symptoms such as hypotension, syncope, and cyanosis,” the study’s corresponding author, Ronna Campbell, MD, PhD, told Medscape Medical News. Campbell is an emergency medicine physician at the Mayo Clinic in Rochester, Minnesota.

For the study, Campbell and colleagues reviewed data on ED visits for adults meeting anaphylaxis diagnostic criteria from April 2008 to December 2022. Older adults were considered to be 65 years or older.

The researchers found that of 1422 emergency department (ED) visits, 212 (14.9%) involved older adults who, when compared with younger adults, were more likely to have anaphylaxis from medications (34.0% vs 21.3%; odds ratio [OR], 1.85; 95% CI, 1.34-2.55) or from IV contrast (13.2% vs 5.6%; OR, 2.50; 95% CI, 1.55-4.04). The older group was 54.7% women. Nearly 65% of the group had a known medication allergy.

Older adults had increased odds of severe anaphylaxis (adjusted OR [aOR], 1.57; 95% CI, 1.12-2.21), involving endotracheal intubation (aOR, 6.24; 95% CI, 2.69-14.48) and admission to the hospital or ICU (aOR, 1.78; 95% CI, 1.19-2.67).

Older adults were also more likely to arrive via emergency medical services (EMSs; 56.1% vs 34.0%; OR, 2.56; 95% CI, 1.89-3.46), but less likely to receive EMS-administered epinephrine (26.0% vs 32.4%; aOR, 0.46; 95% CI, 0.27-0.77).

“Most patients experienced reactions outside the ED, such as after medication, food, or [insect] stings, but some encountered the trigger either in the ED or in other outpatient settings,” said Campbell.

Drugs and Venom, Not Food

“Food is not a predominant culprit of anaphylaxis in older adults,” Moshe Ben-Shoshan, MD, MSc, told Medscape Medical News in an interview. “It’s mainly associated with drugs or with venom.”

Ben-Shoshan, a clinical assistant professor of pediatrics in the Department of Allergy, Immunology, and Dermatology at the Montreal Children’s Hospital in Montreal, Quebec, Canada, is one of the authors of a study published this month in the International Archives of Allergy and Immunology, which similarly found that older adults were at risk of not being given epinephrine when they had anaphylaxis.

Ben-Shoshan and colleagues’ study reviewed data collected between April 2011 and May 2024, for the Cross-Canada Anaphylaxis Registry, which includes five EDs and one EMS across three Canadian provinces.

Of 1135 anaphylaxis cases seen in the ED, the researchers found 90 (7.9%) were in older adults. The median age of this cohort was 70.3 years, and 42.2% were men.

Anaphylaxis in this group was more likely to be triggered by drugs and venom (P < .01) when compared with younger adults.

The most prevalent symptoms noted in the Canadian study for the older cohort were pruritus (55.6%), urticaria (55.6%), breathing difficulties (53.3%), and angioedema (47.8%). Throat tightness was less likely to be associated with anaphylaxis compared with the younger adults studied (43.3% vs 55.3%; P = .03). Gastrointestinal symptoms, including abdominal pain and vomiting were less common in older adults than in younger ones (12.2% vs 23.4%; P = .01).

Food allergies were less common in older adults than in younger ones (13.3% vs 34.6%; P < .01). Drug allergy was also more common in older adults in this Canadian study (28.9% vs 15.2%; P < .01). The prevalence of a known venom allergy was also higher in the older population (6.7% vs 2.4%; P = .03).

Similar to the study in JACI, the Canadian study found older patients were more likely to experience anaphylaxis at home (P < .01) and had higher ICU admission rates (P = .04). Epinephrine, as in the JACI study, was less frequently administered to older patients with anaphylaxis (30.0%).

Implications for Practice

“Even though older adults arrived by EMS more often, they were significantly less likely to receive epinephrine from EMS providers,” Campbell wrote. “This underuse may stem from concerns about cardiovascular side effects or difficulty recognizing the reaction in this age group,” she said.

Ben-Shoshan suggested that cardiovascular comorbidities could have a role in older adults ending up in the ICU after anaphylaxis — “probably because of all the comorbid conditions like high blood pressure or other cardiovascular conditions,” he said in an interview.

Because older adults are, overall, more medically vulnerable than younger ones, Campbell said having a suspicion of anaphylaxis is important.

“Quick recognition and treatment save lives — particularly in this vulnerable group, where delays are more dangerous,” she said. “Complications from epinephrine were very rare and outweighed by the benefits,” Campbell said of her study. “Guidelines emphasize that there are no absolute contraindications to epinephrine in anaphylaxis, even in older patients. It should always be on hand, and early administration is critical to prevent progression to severe or fatal reactions.”

Both Campbell and Ben-Shoshan said there is a need in the medical community for improved EMS and clinician education on atypical presentations of anaphylaxis in older adults, and an emphasis on the importance of early epinephrine use.

“Older adults were less likely to be discharged with self-injectable epinephrine prescriptions or referred to allergy specialists, despite their higher risk of severe reactions,” Campbell wrote. “Addressing these gaps is essential for prevention of future severe episodes.”

Campbell reported receiving royalties from UpToDate and was a consultant for Bryn Pharma. Ben-Shoshan reported receiving grant/research support from Novartis and Sanofi and being a consultant for Novartis, Medexus, Sanofi, Bausch, Miravo, and Stallergenes Greer.