Allergy Causes: The Myths and Facts

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While an extended winter means many seasonal allergy sufferers are still breathing easy, tree pollen is already in the air in much of the country, causing sneezing, itchy eyes and a runny nose, congestion, and other classic allergy symptoms. And the pollen count will only get worse as the weather gets warmer.

According to the American Academy of Allergy, Asthma & Immunology (AAAAI), up to 40 percent of adults worldwide have allergies, including seasonal allergies, and food and skin allergies. And in the U.S., 14 percent of adults and 13 percent of children have physician-confirmed seasonal allergies, according to treatment guidelines published last year in the Annals of Allergy, Asthma & Immunology.

But much of what we think we know about allergies is based on some long-standing myths. Here, the truth behind some common misconceptions.

Myth: We Outgrow Allergies Over Time

The real deal: Not necessarily. Allergies occur when your immune system overreacts to the presence of “invaders” such as pollen, mold, and dust mites. Your system releases compounds that can cause inflammation, excess mucus, and itchiness in your eyes, ears, and throat.

As you age, your immune system may become less robust and less likely to react so strongly to allergens.

“There’s a common perception that as you get older, allergies go away,” says Richard F. Lockey, M.D., director of the allergy and immunology department at the University of South Florida College of Medicine. “There’s some truth to that. But as we see people staying healthy longer into old age, we still see people in their 80s having symptoms or developing new allergies.” In fact, up to 11 percent of people 66 and older suffer from seasonal allergies, making them almost as common in seniors as in children and younger adults.

Myth: It's Easy to Tell Allergies From Other Conditions

The real deal: It's not always easy to determine allergy causes—and that's especially true in older adults, according to UpToDate, which provides evidence-based treatment information to healthcare providers. In seniors with new nasal symptoms—if there isn't a new pet in the home, a move to a new climate, or other obvious triggers—non-allergy causes should be considered.

“Many older people have general nasal stuffiness,” Lockey says, “whether it’s from drugs for high blood pressure or prostate problems, or just from normal age-related changes in the nasal passages.”

So be specific with your doctor about symptoms and when they appear. For instance, itchiness of the eyes, ears, or throat is a classic sign of allergies but usually doesn’t accompany respiratory infections such as colds or flu.

If symptoms crop up at certain times of the year or only when you’re around the family pet, that’s another sign you’re probably dealing with an allergic condition.

In addition, though respiratory infections can cause fever, aches and pains, or yellow mucus, allergies generally don't. And respiratory infections resolve in a week or two, while allergies may persist for longer.

Myth: Allergic Skin Problems Are Usually Seen Only in Children

The real deal: It's true that allergic skin issues such as eczema are common in children. According to the latest data from the National Center for Health Statistics, 12 percent of children have skin allergies.

But allergy-related skin problems can affect people later in life too, as noted in a review published last year.

In fact, according to an earlier review published in 2011, contact allergies—which can cause redness, itching, welts, rashes, and/or hives after touching an allergen—occur more frequently as we age. Typical allergy causes include metals like nickel, perfume, plants such as poison ivy, and latex.

Important to know: Hives can erupt suddenly as a result of any type of allergy, but they can also signal the serious, systemic allergic reaction called anaphylaxis. (See “Treating Allergies Right,” below.) If you have hives and your lips, tongue, or throat feel like they’re swelling, or you’re wheezing, having trouble breathing, or becoming dizzy, call 911. Use an epinephrine injector if you’ve been prescribed one.

Myth: Food Sensitivities Are Food Allergies

The real deal: Not true. A food allergy is an immune-system reaction that can involve multiple organs and systems, and can sometimes be serious enough to cause anaphylaxis. A food sensitivity is most often limited to your digestive system.

An estimated 15 million Americans—approximately 4 percent of children and 1 percent of adults—have a food allergy, and numbers have been rising over the past two decades, according to a review published last year in The New England Journal of Medicine. But many more people may be sensitive to certain foods.

With a true food allergy, your body has made antibodies—which combat substances the body sees as threats—against one or more proteins in that particular food, says Ravi Viswanathan, M.D., an assistant professor in the division of allergy and immunology at the University of Wisconsin School of Medicine and Public Health.

“Every time you eat it, you get hives, swelling, maybe wheezing, chest or throat tightness, shortness of breath, GI symptoms, or dizziness,” he says.

Those with sensitivities, he explains, tend to have gastrointestinal discomfort such as queasiness and bloating, but not necessarily each time they consume a problem food.

If you suspect you have a food allergy or sensitivity, keep a food and symptom diary to share with your doctor. This can help you isolate potential offenders.

Myth: Allergy Tests Are the Only Way to Identify Allergens

The real deal: Not everyone with allergy symptoms needs testing to determine allergy causes, and the results should be seen as only part of the diagnostic picture. A medical history, physical exam, and discussion with your doctor about symptoms and lifestyle habits are also essential.

Allergy tests may be warranted if your doctor can’t determine what’s causing your problem. Testing can be done a couple of ways. With skin testing, an allergist or immunologist applies tiny amounts of possible allergens to pricked skin or injects them under skin (intradermal testing).

If you’re allergic to a substance, your skin will redden, swell, and/or itch within 20 minutes. (For contact allergies, you might be asked to wear a patch containing a potential allergen for two days.)

A review of the research published in 2016 in Allergy, Asthma & Clinical Immunology found that skin-prick tests, usually done on a forearm or the back, can accurately identify the presence or absence of most allergens. (There’s not enough data to draw a conclusion about intradermal tests.)

However, a study published in 2014 in the Annals of Allergy, Asthma & Immunology suggests that sun damage and thinning skin may blunt the reaction to allergens, which could prevent a proper diagnosis.

Alternately, your doctor may draw your blood and order a laboratory test to identify your allergens. Blood tests may be more likely to find allergies where there are none. But doctors sometimes prefer them for those who have a skin condition like eczema or use medication that can interfere with skin tests.

Skin and blood tests for food allergies appear to be incorrect about half the time, so it’s best to use them only for foods you already suspect are triggers for you or your child.

“We recommend against indiscriminate testing because there’s a good chance you could test positive when you’re not really allergic,” Viswanathan says. “We test only for the specific foods that seem to be causing a problem.” In fact, the AAAAI is so concerned about the overuse of those tests that it recently included them in the Choosing Wisely campaign, which highlights unnecessary and sometimes harmful medical care.

If you test positive for a food allergy, your doctor may follow up with an oral challenge, where you eat the food in increasing amounts (under medical supervision) to gauge your response.

Skip the tests you might see advertised on the internet that analyze your hair or your muscle response to allergens. They’re not backed by quality research or evidence. 

Treating Allergies Right

If you know you have allergies, start by avoiding triggers:

Ragweed: Check local pollen levels on the AAAAI's website and try to stay inside when they’re high.

Mold: Avoid leaf piles, ventilate damp rooms, and fix leaks promptly.

Dust mites and pet dander: Keep pets out of the bedroom, vacuum regularly with a low-emission vacuum (see our vacuum cleaner buying guide), cover mattresses and pillows with allergen-proof cases, and wash bedding in hot water.

For more relief, consider:

An over-the-counter antihistamine to reduce symptoms: Newer drugs such as cetirizine (Zyrtec), fexofenadine (Allegra), and loratadine (Claritin)—all available as generics, too—are less likely to cause drowsiness than older drugs. Some people, especially seniors, may still experience drowsiness though, so it's best to use them cautiously.

Steroid nasal sprays: OTC and prescription products such as fluticasone (Flonase, Flonase Allergy Relief, and generic) and triamcinolone (Nasacort, Nasacort Allergy 24HR Relief, and generic) can keep symptoms at bay but can also cause nasal irritation and occasionally nosebleeds, so it's best to stop using them if that occurs.

Immunotherapy: For more bothersome symptoms, your doctor might recommend regular injections or daily under-the-tongue tablets (only for dust mites, grass, and ragweed) that contain small amounts of the offending substances. These can often gradually desensitize you to allergens, but both the shots and tablets can be expensive.

Emergency epinephrine: If you’re at risk of anaphylaxis, a potentially life-threatening reaction to a food, insect sting, or other allergen, you need to have injectable epinephrine (Adrenaclick, EpiPen) on hand.

Additional reporting for 2018 update by Chris Hendel.

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