Can You Develop Allergies as an Adult?

Allergies can pop up at any time in your life
Elderly person suffering from allergies while outside.

One day, you’re happily busting open peanuts at the ol’ ballgame, when suddenly, your lips are itching. It’s never happened before, and you wonder, What that’s all about? Or maybe you recently adopted a new cat and realize your nose has been running since your little fur baby entered the house. What’s going on?

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While you may think of allergies as kids’ stuff, new allergies — to food, the environment and more — can trigger at any time in your life, and for a whole bunch of different reasons.   

We talked with allergist Lily C. Pien, MD, MHPE, about common allergies in adults and why allergies can come on later in life. 

Why we get allergies 

The Asthma and Allergy Foundation of America (AAFA) calls allergies “among the country’s most common, but overlooked, diseases.” 

Allergies happen when your body reacts to a harmless substance, say pollen, animal dander, dust mites or foods. Your body mistakes the trigger for a dangerous intruder and mounts a defense. You release a chemical called histamine that causes symptoms of an allergic reaction. 

Depending on the allergen, you may experience signs of an allergic reaction, like: 

  • Hives
  • Itchiness. 
  • Rash
  • Runny nose. 
  • Scratchy throat. 
  • Swelling. 
  • Trouble breathing. 
  • Vomiting. 

Why people develop allergies is still a topic of debate in the medical world. 

“Allergies are a product of both nature and nurture,” Dr. Pien says. “We know that our genetics can predispose some of us to have an allergy. Exposure to the allergen can turn on allergic antibody production.

“At some point, for some people, re-exposure to the allergen causes clinical allergic symptoms related to the previous allergic antibody production. But the reasons why the clinical symptoms get turned on, when they’ll turn on and for whom are still not well known at this point.” 

Can you develop allergies as an adult? 

One of the most mind-boggling things about allergies is that they can ebb and flow throughout your life, seemingly at random.

Babies with milk allergies often outgrow them. Recent research has shown that with consistent exposure, some kids with peanut allergies may develop tolerance to them.

On the other hand, adults who’ve never had an allergy can suddenly find themselves having an allergic reaction to a trigger that never previously bothered them. Or they can find that things that used to cause reactions just don’t bother them anymore. 

Dr. Pien walks us through some common scenarios and offers up some reasons you may develop allergic reactions later in life. 

Food allergies 

Research shows that about 10% of U.S. adults have a food allergy, and half of those developed during adulthood. Dr. Pien says there are a few reasons you may develop food allergies as an adult.  

One reason is that some food allergies can be related to other allergies you may already know about. 

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“We find that allergies to shrimp are sometimes coupled with a dust mite allergy,” Dr. Pien says. “Some people will already know they have an allergic reaction to dust. Then over time, they find they can’t eat shrimp without a reaction. We don’t know how these allergies might be related, if there is cross-reactivity, or coincidence involved.” 

The same is true for people with allergies to airborne allergens like pollen. A ragweed allergy, for example, can be coupled with oral allergy symptoms to bananas, watermelon and cantaloupe. And allergies to birch tree pollen can be paired with oral reactions to stone fruits, like peaches, plums and cherries.  

That’s because, at the molecular level, there are similarities in the substances found in these pairings. Your body sees them as similar invaders and mounts a defense against them. 

Other times, food allergies in adults may be a matter of long-term exposure. 

“We now know that kids who are exposed to peanuts earlier in life have a better chance of building up a tolerance,” Dr. Pien notes. “On the other hand, we see that adults who never noticed a reaction to a food may suddenly find that their lips swell after eating it. Perhaps they were genetically predisposed to the allergy all along, but it took years of exposure to trigger that response in their immune system.” 

Another factor can be how food is prepared. Dr. Pien says some people who have pollen-fruit syndrome find that they can eat baked apples, but get an oral rash or mouth itching after eating raw apples, especially if they aren’t peeled. 

Food allergies can also come on after a period of “intermittent exposure,” too. That means that if you eat a food relatively consistently, your body can build up a tolerance to that food, even if you’re technically allergic to it. Stop eating the food for some time and that tolerance can fade. The next time you eat it, it can result in an allergic reaction. In such a case, the allergy was there all along, without you even knowing it.   

The most common food allergies in adults include: 

If you notice new symptoms of a food allergy, like swelling or itching of your lips, tongue or throat, talk with a healthcare provider. Depending on your type of reaction and the severity of the reaction, they may recommend avoiding the allergen. 

Seasonal allergies 

Trees, pollen, grass and ragweed are some of the most common allergens. People with seasonal allergies can find that spring blooms can cause itchy eyes and a runny nose.  

Dr. Pien says new allergic reactions to outdoor allergens can happen after moving to a new region, exposing you to a new ecosystem.  

Another explanation for adult-onset seasonal allergies can occur related to changes in medications you take. Or, to be specific, if you stop using a certain medication. 

Antihistamines are among the most common treatments for seasonal allergy relief. Certain antihistamines, though, can also be prescribed for conditions like anxiety and insomnia  

“Some people take antihistamines without realizing that’s what they are,” Dr. Pien states. “You think of it as your medication for anxiety or another condition. But when you stop taking it or change to a new medication, you suddenly feel the effects of seasonal allergies that you didn’t even realize that the medications were masking.” 

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Pet allergies 

Maybe you grew up in a home with pets and never had an issue. Now, as an adult, you find that petting a cat or being in a home with a dog brings on the sneezes and itches. 

Pet allergy symptoms can develop in adults for a variety of reasons. It could be that your new dog sheds more than others you’ve lived with. Or maybe the cat you adopted is male, whereas you grew up with female cats. (Fun fact: Researchers say you’re more likely to be allergic to male cats than females.)   

Or maybe you’re spending more time with your pets now as an adult than you did as a kid. Perhaps they sleep in your bed now, as opposed to in your parents’ room when you were growing up. That could mean you’re being exposed to more allergens now than you were in the past — and your nose is the worse off for it.  

Allergies to stings 

The first time you’re stung by a bee, wasp or other stinging insect, you probably won’t have much of a reaction (allergy-wise at least. The torrent of curses you use to cope with the pain is a separate issue.) Future stings, though, could be another story. 

“For some people, an allergy test may show they have the IgE (the antibodies produced by the immune system as a reaction to allergens) but it’s not clinically relevant,” Dr. Pien says. In other words, your body may mount a defense against a bee sting — or any other allergens — but you don’t feel any symptoms of an allergic reaction.  

If you get stung again in the next month or so, or if the next time you’re stung, you’re stung multiple times (ouch!), you may show symptoms of an allergic reaction. That’s because there may be more IgE coursing through your body this time around. So, what may seem like a sudden allergy may really have been there all along. All it took was enough exposure or more exposure.  

Talk with a healthcare provider 

Allergies can’t be cured, but they can be managed.

If you think you’re developing a new allergic response, Dr. Pien says to talk with a healthcare provider. 

“New allergies may take three to five years to develop, so if you haven’t had an allergy test recently, your provider may want to perform one,” Dr. Pien says. “They’ll be able to help you identify any allergies you have and discuss approaches to managing them.”  

Common treatment options for allergies include: 

  • Antihistamines. 
  • Allergy shots (immunotherapy). 
  • Avoidance of allergens or gradual sensitization to the allergen. 
  • Decongestants. 
  • Nasal sprays and nasal steroids. 

Allergies can definitely develop later in life. Sometimes, they’ve been lurking in the shadows all along waiting for the right trigger. Other times they just happen.  

But some allergic reactions can be serious and even life-threatening, so if you suspect you have an allergy, talk with a healthcare provider before attempting to diagnose or treat yourself. 

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