Could It Be an Allergy?

Telling the difference between an allergic reaction and something else can be tricky.

From the WebMD Archives

Wondering if your nagging cold is actually an allergy? Or what about your new skin cream that made your hands break out? Distinguishing an allergy from a non-allergic condition is not always a clear-cut task. But knowing the difference can sometimes help you solve what's ailing you, which in turn could mean faster relief.

Mary Fields knows just how difficult pinpointing an allergy can be. The 64-year-old Bronx resident tells WebMD she was convinced her frequent hives were caused by something in her diet.

"At first I thought I was allergic to chocolate, so I stopped eating that, but it still came back and even started to spread from my arms and legs to my back and thighs," says the retired nurse's assistant.

Fields' dermatologist referred her to allergist David Resnick, MD, FAAAAI, who ran a battery of allergy tests on her. "All the tests came back negative. This isn't an allergy. Her hives got increasingly worse with stress, which might be a part of it. But her symptoms are idiopathic, meaning their origin is unknown," says Resnick, who directs the allergy division of New York-Presbyterian Hospital/Columbia University Medical Center.

"I was a little surprised it wasn't food," says Fields, who says the hives started when her husband was diagnosed with a heart condition and needed to have a pacemaker implanted. "I was going through a lot of stuff but I didn't realize I was worrying. So I'm trying to keep myself calm now, to start releasing some of the stress, and I guess I'll see if that stops the rash."

Mistaking Allergies: Easy to Do

Fields isn't alone in thinking an allergy was at the source of her outbreaks. Many people see just about any bad reaction to be an allergy, which isn't surprising, since more than half of all Americans test positive for at least one allergen, according to the American Academy of Allergy Asthma and Immunology.

Technically speaking, a true allergic reaction happens when the body mounts an unusual immune response to something that's normally harmless. Most allergy tests check for higher levels of antibodies known as Immunoglobulin E (IgE) in the blood, which are launched by the immune system to fight the invading substance.

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As in Fields' case, food allergy is one of the more regularly misrecognized types of reactions among people trying to self-diagnose. "In general, it's more common to experience food intolerance than an actual allergy," says allergy specialist Alan Goldsobel, MD, FAAAAI. "For the majority of people who believe they have one, when they get tested it's not a true food allergic reaction," says Goldsobel, who is a clinical professor at the University of California, San Francisco, and adjunct associate professor at Stanford University Medical Center.

Goldsobel points out that although nearly 20% of adults claim they have a food allergy, studies show that only about 2% of adults have a true food allergy based on test results. And whereas almost 30% of parents say they think their child has a food allergy, the actual rates range from only 6% to 8% among children under age 6.

Regardless of whether it's food or other types of allergy, specialists say they rarely ever have to convince someone they have one. "It's always the other way around. I'm usually trying to persuade patients that they aren't allergic to something," Resnick tells WebMD.

How to Recognize an Allergy

Although you can't always tell the difference between an allergy and something else for sure, here are some general tips to help distinguish an allergy:

Make a checklist of symptoms. Differentiating nasal allergy problems from cold or viral conditions spells relief for most people because nasal allergy symptoms (also known as allergic rhinitis) affects between 10% to 30% of all adults, but treatment can reduce those symptoms in about 85% of those sufferers. So if you're not sure if you have one or the other, inventory your symptoms.

"If the list encompasses fever, greenish or yellow-colored mucus, or joint and muscle pain, then it's more likely a cold," Resnick says. But if you've got sneezing; itchy, red, or watery eyes; clear nasal discharge; or your nose, throat or ears feel scratchy -- then he says you're probably dealing with an allergy.

Timing is everything. The duration and time of year the symptoms occur can be strong clues to identifying their root cause. "Once you find that the symptoms are lasting two or three weeks or even a few months, we say it's probably not a routine cold," Goldsobel says.

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If nasal allergy symptoms get worse in the spring or fall when pollen counts are generally higher, then it's more likely to be an allergy. "However, if they happen all the time, then you still have to figure out if you have a year-round allergy, which is commonly due to indoor allergens like dust, pets, or cockroaches," Resnick says.

It's not just a gut feeling. "With food allergy, you're not just looking for gastrointestinal symptoms like stomach cramps, diarrhea, bloating, or upset stomach -- you're also looking for a rash, or respiratory symptoms – something that goes beyond the GI tract," Goldsobel says. The reason? Food allergies are usually a multiple system reaction. So if just one organ system appears to be involved, it's more likely to be something else, such as an intolerance, insensitivity or even food poisoning.

Rule out brain and nervous system disorders. According to the National Institute of Allergy and Infectious Diseases, certain disorders often thought to cause food allergies either do not have enough research to support a link, or they have been disproven to be related. Among them are migraine, hyperactivity in kids, and certain disorders related to brain and central nervous system functioning -- mainly characterized by symptoms of fatigue, nervousness, and trouble concentrating combined with headaches. So most likely, you can eliminate food allergies from the list of possible culprits for these symptoms.

"A lot of parents come in saying their child's behavior or mood or irritability is due to a food allergy, and they're basically wondering what food is going to make them turn into a well-behaved, calm child – that's really what's being asked," Goldsobel says. "Unbiased research studies show that in the absence of other symptoms, just effects on the brain in terms of thought processes, mood, or behavior are extremely uncommon as a manifestation of food allergy," he says.

When You Can't Figure It Out on Your Own

Sometimes it's nearly impossible to tell if you're having an allergy short of being examined by a doctor. The prime example: a skin allergy from contact with a substance.

"For the person who is having the symptoms, there is probably no defining difference between allergic contact dermatitis and irritant contact dermatitis – both are going to irritate the skin the same way," Goldsobel says. Unless you're tested, it's not really possible to tell if you're having an immune response or not. But in the end, the solution is usually the same – avoid contact with whatever is causing the irritation.

If allergy symptoms continue to bother you and at-home treatments (including avoidance of symptom triggers) fail to work, or if you're still unable to tell if you're having an allergy or something else, then it's time to talk to your primary physician or see an allergist for a full evaluation.

WebMD Feature Reviewed by Laura J. Martin, MD on March 04, 2010

Sources

SOURCES:

Davis, C. Current Problems in Pediatric and Adolescent Health Care, November 2009; vol 39: pp 236-254.

Sampson, H. Journal of the American Medical Association, Dec. 10, 1997; vol 278: pp 1888-1894.

David Resnick, MD, FAAAAI, director, allergy division, New York-Presbyterian Hospital/Columbia University Medical Center.

Alan B. Goldsobel, MD, FAAAAI, clinical professor, University of California, San Francisco; adjunct associate professor, Stanford University Medical Center; Allergy and Asthma Associates of Northern California.

American Academy of Allergy Asthma and Immunology.

National Institute of Allergy and Infectious Diseases.

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