Why get tested?
If you have a chronic runny nose, seasonal symptoms, itchy skin, or you’ve had a reaction to food, I recommend you get tested to identify what you’re specifically allergic to. Many patients self treat their allergy symptoms with over the counter allergy relief medications, or prescription allergy drugs. But if you find the source of your allergies, through diagnostic testing, you may be able to do something to prevent the symptoms in the first place—and reduce the amount of medications you’re taking.
All asthma sufferers should be tested for allergies, according to recommendations from the National Institutes of Health, because 50 to 60 percent of adults with asthma and nearly 90 percent of children with asthma have underlying allergies that may contribute to their condition.
There are two ways to be tested for allergies. After taking a complete history, many allergists use the traditional skin-prick method to test for specific allergens. But some allergists, including myself, have switched to highly sophisticated blood tests that measure levels of specific IgE antibodies, giving a more accurate diagnosis.
Skin Prick Test
The traditional way to test for allergies, a drop of liquid allergen is placed on the surface of the skin and gently pricked with a plastic toothpick device. The allergist can test for mold, dander, pollen, foods and just about any other type of allergen. It can take up to 20 minutes to get a reaction. If the skin develops an itchy, red wheal (bump), this could indicate that you have IgE antibodies to the allergen being tested, and you might be allergic, depending on the severity of the reaction and your symptom history. It’s important to remember to stop taking antihistamines at least three days before being tested.
Allergy Blood Test
Today, you get a simple blood draw, with a single needle prick, and test for any number of allergens. Allergy blood tests have been around for decades, but advances in technology have made them much more accurate than in the past. Studies show they are as accurate as skin prick testing. The blood test measures the level of IgE to specific allergens in your blood.
Your blood is taken and sent to a lab. A few days later, your allergist receives a score, reflecting how much IgE, if any, you have, and uses that number along with your symptom history to determine what allergies you have. One advantage of blood allergy testing is that you get a quantifiable number, which is less subjective than examining the size of a wheal or the degree of redness on your skin. In fact, studies have determined cutoff scores for several food allergens like milk, egg, and peanut, making it easier for allergists to diagnose with certainty. If your score is above the cutoff, your risk of being allergic is very high. Another advantage of blood allergy testing is that it’s safe, because you don’t have to expose your body to the allergen as you do with skin prick testing. I use the ImmunoCAP test (by Phadia), which has been shown to be the most reliable.
Component Testing for Food Allergies
A new type of blood test called component-resolved diagnostic testing (CRD) was recently introduced by Phadia, and it more accurately determines which food or other allergen is connected to your symptoms. CRD uses sophisticated microarray technology to isolate single molecules in allergens rather than using the whole substance like grass or peanut. This helps tackle one shortcoming of existing blood allergy tests. Often some of the components of one allergen, like peanuts, are similar to components of another allergen, like grass, so a child may test positive for peanuts but actually be allergic to grass. It’s called cross sensitization.
By using single specific molecules, CRD reduces your chance of being misdiagnosed with an allergy due to cross sensitization. Another important use of CRD is that it can identify which proteins in peanut, for example, are more likely to cause a severe reaction. Not everyone with IgE to peanuts is allergic and not all allergic people are at risk of anaphylaxis, but it’s difficult to sort out who’s who based on the existing tests. But researchers have identified which proteins are more dangerous than others, and CRD can now test for them.
Component testing is also important in differentiating oral allergy syndrome, which causes redness and swelling in the mouth from severe anaphylaxis to a food. Many patients that are allergic to fruits such as apples, cherries, peaches, or kiwi aren’t sure if they are also at risk of anaphylaxis. CRD can pick out the proteins that are likely to cause a more serious reaction from the more benign proteins that cause oral allergy syndrome.
If you have a child that is diagnosed with a number of food allergies, but he has a vague history of symptoms to that food, ask your doctor to order the test through the reference laboratory called PiRL (Phadia immunology reference laboratory).
To get tested contact us today.