Health

A Simple Blood Test May Be An Alternative To Traditional Allergy Testing

By CBSNews.com staff CBSNews.com staff

January 31, 2002 / 8:41 AM EST / CBS

As many as 50 million Americans have food and seasonal allergies. Doctors traditionally use skin tests to diagnose allergies. The procedure involves placing an allergen on the skin and pricking it with a needle to determine if the patient has an allergic reaction. Now, a simple blood test that looks for antibodies to a particular allergen in the blood may be a viable alternative.

Dr. Bernadine Healy talked with the Saturday Early Show about this new test and gave us some tips on how to minimize the suffering from seasonal allergies, which typically begin in the spring.

What causes allergies?

When an allergen-sensitive person sniffs specks of pollen, dander, or mold, the immune system goes on red alert. It cranks out antibodies that glide through the bloodstream, attaching to cells in the nose, throat, and lungs and stirring them up to release chemicals like histamine. It's these panicked secretions that leave you with a runny nose, swollen eyes, and a cough. Every allergen induces a specific kind of antibody that finds a home in your body and then waits for a perfect match. When everything clicks, like a lock and key, the sneeze fest begins.

What are the advantages of this new blood test over the skin test?

The biggest advantage is that it causes none of the discomfort of skin tests, such as itching and the painful pricking. The allergen is placed on the skin and pricked with a needle to determine if the patient has an allergic reaction. It's often done as many as 20 times on one arm. Parents especially may find it difficult to hold down their children when they're getting pricked 20 or more times in the arm. However, the downside is that results for the new test might take a couple of days to get back, instead of the typical on-the-spot results of skin tests.

Is this blood test more effective?

A study published 2 years ago compared the accuracy of skin testing and blood testing for cat allergy. Researchers found that both tests were about equal. However, some doctors still prefer skin testing because it shows a direct response between a patient and an allergen, whereas a patient may have antibodies in his blood, but still not show a real-life allergic reaction to the substance. And, many insurance companies still tend to favor skin testing. But keep in mind, skin testing is far from foolproof, too. You need to take into account any conditions like eczema or medications like antihistamines or antidepressants that can block the body's sensitivity.

Many people get really bad allergies in the spring, and we have a list of things people can do to ease the suffering:

Dust and vacuum often.
Wash bedsheets at least once a week.
Keep air in house dry.
Install HEPA filter.
Ban pets from bedroom.
Wash pets once a week.

To stop the allergy attacks, you need to reduce your exposure to the things that trigger them. If you hae dust and mold allergies, put on a mask and clean your house once a week or have someone else vacuum and dust for you. Also, muggy air helps spores grow, so consider using a dehumidifier to keep things dry. You might also want to install a HEPA or electrostatic filter in your heating system to remove many allergies. But remember to change the filter often. If you have pets, decrease the dander by banning pets from the bedroom and wash pets once a week since they bring in all sorts of stuff.

For some people, spring isn't the only time they get allergies, right?

That's right. Some people get them year round, and people with asthma can have allergies triggered not by allergens but by physical stimuli such as cold and exercise. This is especially important for parents who might send their child out to play in the winter. The cold air could trigger the sneezing and wheezing. So a scarf might help to warm up the air for the child.

For relief, should go for an over-the-counter medicine or see a doctor for a prescription?

If you have occasional symptoms, try an over-the-counter drug. Antihistamines can tame coughs, itchy eyes and sneezes. However, most cause drowsiness. You might also want to use a decongestant to clear yourself up. Also, the more you use the drug, the less effective they get over time. If your allergies are persistent, ask your doctor for a nonsedating antihistamine like Allegra, Claritin, or Zyrtec. They are just as effective as over-the-counter versions but without the drowsiness. Other alternatives include a nasal steroid spray such as Flonase or Nasonex. But these take 3 to 10 days to kick in, so you need to start before symptoms get out of control.

Do allergy shots help?

Allergy shots raise your body's tolerance to allergens. Research suggests the shots have long-term, perhaps even permanent, benefits. But the immunotherapy is intensive: weekly shots for 4 to 6 months, then a shot every 3 weeks for a few years.