New research identifies an increase in pediatric cases of anaphylaxis in response to peanuts and unknown nuts during Easter and Halloween.

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A new study concludes that Easter and Halloween are associated with an increase in cases of nut-related anaphylaxis — a type of severe allergic reaction.

The research, which features in the journal CMAJ, may help public awareness campaigns focus on particularly risky times of the year.

According to the American Academy of Allergy, Asthma & Immunology, anaphylaxis is a potentially life threatening allergic reaction. The most common reactions are to insect stings, latex, medications, and types of foods.

If a person is allergic to something, their immune system overreacts to a usually benign substance that the body mistakenly perceives as a threat. This reaction can cause a range of symptoms that are often localized to the affected area, such as itching, swelling, and sneezing.

If a person has a more severe allergic reaction, they may experience symptoms in more than one part of their body, and the risk linked to these symptoms increases.

Scientists have defined anaphylaxis as a severe allergic reaction that involves two or more organ systems or hypotension, which is abnormally low blood pressure.

A person may begin to experience the symptoms of anaphylaxis 5–30 minutes after coming into contact with the substance to which they are allergic.

These symptoms can include a red, itchy rash, swelling around the throat or on other parts of the body, loss of consciousness, difficulty breathing, and nausea and diarrhea.

A study looking at data from 2009–2010 suggested that 8% of children in the United States had a food allergy, the most common being a peanut allergy. Of the children with a food allergy, almost 39% had a history of severe reactions.

Allergies to tree nuts, which include walnuts, almonds, cashews, hazelnuts, pecans, and pistachios, are also among the most common food allergies.

Researchers have suggested that the prevalence of food allergies among young children is increasing. If parents or caregivers are aware of the allergy, protecting the child while they are at home relies on them being cautious about what the child eats.

However, the tradition of gift-giving, often in the form of candy, means that holiday seasons pose a particular challenge for parents and caregivers trying to control what their children eat.

In the present study, the researchers wanted to see whether there was an association between particular holidays that people typically celebrate in Canada and the rate of children presenting at hospitals with anaphylaxis in response to peanuts, tree nuts, or unknown nuts.

To do this, they analyzed data covering the period between April 15, 2011, and January 31, 2020, from pediatric emergency departments in four Canadian provinces.

They focused in particular on the holidays of Halloween, Christmas, Easter, Diwali, Chinese New Year, and Eid al-Adha. The researchers looked at data from the day prior to the holiday, the day of the holiday, and the 3 days following the holiday.

In total, the researchers identified 1,390 cases of anaphylaxis relating to peanuts, tree nuts, or unknown nuts. Anaphylaxis was determined both prospectively, by the doctors formally identifying it at the time, and retrospectively, by the researchers analyzing the charts of the patients.

Overall, 62.2% of the children presenting with nut-induced anaphylaxis were boys, and the children had a median age of 5.4 years.

The researchers found that, compared with the rest of the year, peanut-induced anaphylaxis increased by 85% during Halloween and 60% during Easter. Anaphylaxis in response to unknown nuts increased by 70% during Halloween and Easter.

The researchers found no significant change in the rate of nut-induced anaphylaxis for Christmas, Diwali, Chinese New Year, or Eid al-Adha.

According to Mélanie Leung, a fourth-year medical student at McGill University, Canada, and co-author of the study, “[t]he difference in the anaphylaxis incidence among holidays may have been due to the social setting in which each holiday takes place.”

“At Halloween and Easter,” Leung continues, “children often receive candies and other treats from people who may be unaware of their allergies. The absence of such an association at Christmas may be because Christmas is a more intimate celebration among family members and close friends, who are more vigilant regarding allergen exposure.”

For co-author Dr. Moshe Ben-Shoshan, a pediatric allergist and immunologist at the Montreal Children’s Hospital of the McGill University Health Centre (MUHC) and a scientist at the Research Institute of the MUHC, the findings suggest that targeted information regarding nut allergies may be valuable:

“Our findings suggest that educational tools to increase vigilance regarding the presence of potential allergens are required among children with food allergies, their families, and laypeople interacting with children who have food allergies. Newer strategies targeting intervals associated with high anaphylaxis risk are required.”

– Dr. Moshe Ben-Shoshan