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Why Do I Suddenly Have Allergies?


Yep, it's possible to develop allergies as an adult.

Woman blowing her nose

Bad news: it is possible to be blissfully free of allergies for decades and wake up one morning to what feels like one. Whether the culprit is something in the air (like pollen or mold) or something on your plate (like tree nuts or shellfish), dealing with allergy symptoms can come on at any age. 

Technically speaking, it’s not a new allergy, says Jonathan A. Bernstein, M.D., an allergist and a professor of medicine at the University of Cincinnati College of Medicine in Ohio. It's more likely that you've had the allergy for a while, but you're only now experiencing symptoms. So, what gives?

Why do people get allergies?

Think of an allergy as your body's misguided attempt to protect you from what it (wrongly) believes to be a harmful substance. When you’re exposed to an allergen, your immune system identifies it as an invader and reacts by producing antibodies, which then travel and activate allergy cells, which release chemicals like histamine into the bloodstream. Once the chemicals are released, you’ll develop symptoms such as sneezing, itchy skin, or swelling, depending on the type of allergy you were exposed to.

What's with the delayed reaction?

There's a process that can occur in the body called sensitization, Dr. Bernstein says, where your body produces an antibody after having contact with an allergen, but you don’t experience symptoms. For instance, as a child, maybe you were once near a friend's cat and didn't experience any symptoms at the time, but without realizing it, your immune system overreacted to proteins in the cat's urine, saliva, or dander and produced antibodies, which sat inside your body and waited. When you’re older, perhaps your roommate adopts a cat and that re-exposure suddenly activates those dormant antibodies, thus developing an allergic reaction. In other words, sensitization is the first (and silent) step in a chain reaction that leads to symptoms, and the two stages of that chain reaction may happen years or even decades apart. Researchers are still a bit unclear on exactly how this happens, especially since some people may have many repeated exposures before developing allergy symptoms, Dr. Bernstein adds.

How common are allergies?

Roughly 50 million Americans have some form of allergic disease and that number is on the rise. According to Dr. Bernstein, it’s not fully understood why one person becomes sensitized or symptomatic, but another person doesn't, but it’s likely due to a combination of genetic and environmental factors. "If one parent has allergies, your risk is 25 percent and if both parents have them, your risk is over 50 percent," he adds.

I think I have an allergy. What symptoms should I look out for?

First of all, it’s important to note that only a doctor can diagnose an allergy. And allergic reactions—no matter when they strike—can take a lot of different shapes. You could experience sneezing, nasal stuffiness, runny nose, and drainage associated with allergic rhinitis, or asthma-like symptoms such as coughing, chest tightness, and wheezing. Allergies can trigger atopic dermatitis, which leads to itchy, dry, eczematous skin. Food allergy symptoms can also occur later in life and may include tingling in the mouth, hives, swelling in the mouth or face, abdominal pain, and dizziness. In some cases, allergy symptoms can be mild, but in others, they can be severe; some people may experience anaphylaxis, a life-threatening reaction (commonly from bug bites, foods, or latex) that cause serious symptoms, like shortness of breath, tightness in the throat, or vomiting and diarrhea.  

If I notice symptoms, what should I do?

If someone is having a severe reaction, call 911 immediately. For more mild symptoms, ask your primary care provider for a referral to an allergist/immunologist. This type of specialist can provide testing, such as a blood test or skin prick, to help figure out if what you’re experiencing is indeed allergies. "A lot of people think they have allergies, but they may actually have other conditions that mimic the symptoms of allergies," Dr. Bernstein says, such as a cold, asthma, or eczema. "It's important to differentiate these conditions because they're treated quite differently." Once you’re diagnosed with your allergy, your doctor will provide a treatment plan for you, in the form of medication or discussing the next steps on how to prevent contact with the allergy.