Why adults can develop new allergies – 04/24/2023 – Equilibrium

Lu Morales, 32, grew up eating a wide variety of Mexican seafood dishes. But at age 25 a “to-go” meal of egg rolls and prawns suddenly gave him anaphylactic shock, an ambulance ride to the hospital and a diagnosis of a seafood allergy.

Morales, who uses gender-indefinite pronouns, says the curlers caused him to cough, wheeze and red, puffy eyelids. Now, he says, seafood is completely off his menu.

While most people don’t experience the gain — or loss — of allergies in adulthood, it’s not uncommon either, says Shradha Agarwal, an allergist and immunologist at the Icahn School of Medicine at Mount Sinai Hospital in New York City. Why allergies wax or wane, especially in adulthood, is not widely understood by scientists.

“There’s a lot of mystery in allergies,” points out Agarwal.

What the Experts Know

Allergies come in many forms and usually develop when your immune system mistakenly treats a harmless allergen like pollen or pet dander as a threat, Agarwal points out. It then reacts every time it encounters that allergen, with symptoms that can range from coughing, sneezing and itching to more severe reactions including hives, vomiting, difficulty breathing and loss of consciousness.

The causes of allergies are complex, says Corinne Keet, professor of pediatric allergy immunology at the University of North Carolina School of Medicine — it depends on your genes, what types of allergens you’re exposed to and when.

But experts think that, in general, things that disrupt your immune system — like puberty, pregnancy, transient or chronic illnesses or organ transplants — “can change your allergic responses to things you tolerated before,” Keet points out.

Experts don’t know how common it is to develop allergies in adulthood, says Ruchi Gupta, a professor of pediatrics who specializes in allergy at Northwestern University Feinberg School of Medicine, although we do have some data related to food allergies. In a survey of more than 40,000 US adults published in 2018, Gupta and his colleagues found that about 45% of those who had food allergies developed at least one new food allergy in adulthood. Of this group, a quarter never experienced food allergies as a child.

An important question for researchers, Gupta points out, is what exactly might cause adults to develop an allergy to a food they ate before. Right now, she says, we don’t know.

Jyothi Tirumalasetty, an allergist and assistant clinical professor of medicine at Stanford University, has seen patients of all ages develop all kinds of new allergies, including some to common allergens such as pollen, pet dander, or tree nuts.

What about allergies that disappear?

“Losing” an allergy, or becoming “desensitized” to an allergen, happens all the time, Tirumalasetty points out, especially near or after middle age. Our immune responses “calm down,” becoming weaker and less vigorous as we age, she says.

Some allergies are more likely to “resolve” than others, Keet points out. Most penicillin allergies go away with time, and seasonal allergies tend to lessen with age, she says.

While it is much less common to develop certain food allergies, such as to nuts, fish and shellfish, says Gupta, an estimated 50% to 80% of children with milk or egg allergies outgrow them by age 10.

A common way people discover environmental allergies is by moving to a new area and encountering pollen they’ve never been exposed to, says Agarwal. This wouldn’t technically be a “new” allergy, she says, but it’s a distinction that can make research in this area challenging. Likewise, moving away from these places can bring relief.

Molly Thessin, 30, who grew up near Nashville, Tennessee, says she had year-round pollen allergies as a child and had to take antihistamines regularly to ease her symptoms. That all changed when she moved to Dallas at 23.

“I stopped taking allergy meds for the first time in my life and was completely fine”, points out Thessin.

A few years later, she moved to New York, where she currently lives, and the allergies returned. Turns out, she’s allergic to most trees and plants in the northeastern US, as well as cats, dogs, mold, and cockroaches.

What about prevention?

As for whether there’s anything adults can do to prevent new allergies from developing, Agarwal says, experts don’t have the answer.

The only allergy prevention research at the moment is focused on preventing food allergies in children, Gupta points out, which has little to do with preventing new allergies in adults.

Ultimately, Keet says, you can’t really control whether you develop a new allergy as an adult. So, she says, “I wouldn’t worry about it.”

Translated by Luiz Roberto M. Gonçalves