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Welcome to the new Thursday edition of the Future Coach newsletter. This week, I'm answering your question about food allergies.

A reader asks: Can adults suddenly develop a new food allergy?

I wrote this week about how to protect kids at school from dangerous allergic reactions to food — and why banning nuts doesn’t work. But adults can be at risk, too. “New food allergies can develop at any age,” write the authors of a 2020 peer-reviewed article.

About 7 percent of adults surveyed reported a medically diagnosed food allergy, reports the Centers for Disease Control. Few comprehensive studies exist about adult-onset allergies, but researchers at Stanford found nearly half of adults with food allergies developed them after age 18, sometimes after years of eating the same food without problems.

The most common allergies among adults? Shellfish (2.9 percent), milk (1.9 percent), peanuts (1.8 percent), tree nuts (1.2 percent) and fin fish (0.9 percent), according to a 2020 study. While many allergies persist, allergies can emerge or resolve at any age. Their prevalence changes over time. Milk is a more common allergen among children, but it’s more likely to resolve before adulthood, along with egg, wheat and soy. Peanut, tree nuts, fish and shellfish allergies are the most likely to persist. While most childhood allergies are in boys, this flips in adulthood when women predominate.

Why do adults develop allergies? Allergies are an immune response. The most severe food allergies tend to be the body’s overreaction to a protein. In the most common form, antibodies target these proteins as threats, prompting the immune system to flood the body with chemicals like histamine and potentially trigger a severe reaction. Sensitivities may develop slowly before exercise, alcohol, viral infections or even an anti-inflammatory drug like Advil and Motrin — amplifies reactions or lowers the threshold for a reaction, revealing undiagnosed allergies.

There’s a new allergy on the block many are acquiring as adults: alpha-gal syndrome, also known as red-meat allergy. First identified in the early 2000s, the CDC now estimates 450,000 people may be affected, although some people may carry the antibodies without symptoms.

Alpha-gal syndrome is associated with tick bites, especially from the lone star tick, concentrated in the Southeast. A sugar molecule in the tick’s saliva provokes an allergic reaction. The same molecule exists in beef, pork, lamb and other mammalian meats, as well as dairy and gelatin.

If you suspect you have a new food allergy, confirm it with an allergist. Don’t experiment by trying the food again. An allergist can use skin or blood tests and review your clinical history to identify potential triggers. If inconclusive, a medically supervised oral food challenge is the most definitive test.

If you are diagnosed with a food allergy, the risk of anaphylaxis — a violent, potentially life-threatening reaction — isn’t high for most people but still worth taking seriously, allergists say. Only epinephrine, also known as adrenaline and typically injected with an EpiPen, can stop the most serious reactions. And while adult-onset allergies are real, a reaction is a reason for medical investigation, not proof of a new allergy.

Many of you wrote to ask why children now have so many allergies. It’s a story of well-intentioned advice outrunning the evidence.

In 2000, parents of children at high risk of allergies were advised by the American Academy of Pediatrics to delay introducing peanuts and seafood until age 3 to reduce the risk of new allergies emerging. That guidance was based on the plausible but unproven assumption that delaying exposure to potential triggers would prevent new allergies.

The academy withdrew that advice in 2008 and when better data came along, it pointed in the opposite direction: Children were 81 percent less likely to develop a peanut allergy if they began eating peanuts within their first year rather than wait, according to a randomized trial published in 2015. Similar preventive effects were later seen with eggs.

That confusion had consequences. As I wrote earlier this week, food allergies reported by parents rose by about 50 percent between 1997 and 2008. Peanut allergies more than tripled.

The academy began encouraging earlier introduction of allergens in 2017. As a result, an estimated 57,000 children did not develop peanut allergies over the next three years, a study published last year estimated.

Today, egg, not peanuts, is the most common allergen among children under 3.

Column  Michael J. Coren Schools should stop banning peanuts. Here’s what really keeps kids safe.

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Send your questions to me at futurecoach@washpost.com. I read all your emails.

See you next week,

Michael Coren, Future Coach

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