Q. My son was diagnosed with peanut allergy by screening blood testing when he was 18 months old (done for a family history of food allergy in first cousins) but he never had a major reaction to peanut before the diagnosis, and nothing has happened since. He is now 5 years old. He has had cookies that were made in a facility where peanuts are present, without any reaction. He recently had a negative skin test for peanut and his last blood test level was 2.3. I was told that my son should continue to avoid peanuts. However, I recently read about a new kind of blood test for peanut allergy, and I am wondering if this test could be helpful for my son?

A. Peanut allergy seems to be on the rise in the US over the past decade. While there are some promising treatments being researched, the current standard of care is complete avoidance of peanut. Because this restriction can have such a major impact on everyone involved, it is very important that you receive an accurate diagnosis. Peanut allergy affects most areas of a person’s life, from the home setting, to play dates, to school, to dining out and beyond.

The most important factor in making an accurate diagnosis of peanut allergy is the actual history of the type of reaction that occurred upon consuming a peanut. Specific IgE blood tests (like ImmunoCAP, a common test) and skin prick tests are used in combination with the clinical history to make a diagnosis. In some cases an allergist-supervised oral food challenge is recommended, and this is, in fact, considered the “gold standard” for accurate diagnosis of allergy to peanut. (This same approach is applied to any possible IgE-mediated food allergy, not just to peanut.)

One problem that allergists face is that some people do not have a clear-cut history of reaction to peanut. Situations that allergists see frequently include:

  • Subjective symptoms - “I feel funny when I eat peanuts”
  • Mild symptoms - “My throat gets scratchy...”
  • Non-specific symptoms - “My stomach hurts...”
  • Unclear history of eating peanuts - “I ate a granola bar at a friend’s house”
  • No history of eating the food - “We have just been avoiding feeding our child peanuts due to other allergies/family history”

In these cases, allergists will typically perform a skin prick test to gain more information. If the skin test is negative, a specific IgE blood test such as ImmunoCAP test can be ordered to gain more information. If the test comes back “negative” (meaning complete absence of peanut-specific IgE or a very low positive result with no history of anaphylaxis or other serious reaction), an allergist will often proceed to an oral food challenge in the office to confirm the test results,

However, if the first blood test comes back positive, yet the clinical history is vague or indicates a mild reaction history, a new test, called the peanut "component test", can be ordered to gain more information in this situation. This component test - the one you are asking about - can determine which specific peanut proteins are triggering the positive test results. It is important to note that there are many smaller protein fragments that make up a whole peanut. Thus, when a person reacts to peanut, he or she may be responding to one or more different protein fragments in the peanut. Determining which of these protein pieces are causing the reaction is important, as some (scientific names “Ara h 1”,” Ara h 2”, and “Ara h 3”) carry more risk than others. Thus, if these specific tests are negative, there is less risk, and if positive, there is more risk. This will help guide whether an oral food challenge would still be okay (despite the positive initial peanut blood test).

Given your son’s unclear history of reaction to peanut, we would recommend that you speak to your allergist about the peanut component test and a possible oral food challenge depending on the results of the test. The information gained from the test will be helpful to you, either way!

Q. I have asthma and was sent to an ENT because of a persistent sinus infection. The ENT did surgery on my blocked passages, which has helped some. He also did allergy testing, to 19 allergens, and told me I was highly sensitive to all of them. My question is - would an allergist test for and treat more allergens than the ENT?

A. These positive tests are only important if they match your personal allergy medical history. This correlation has far greater importance than the number of tests done, which can vary based on one's history, geographic location, etc. For example, a positive skin test to ragweed pollen is only meaningful if you experience allergic nasal and eye symptoms during the ragweed pollen season in the late summer.

Q. I have asthma and was sent to an ear, nose, and throat (ENT) surgeon (by my pulmonologist) because of a persistent sinus infection. Because of blocked passages, the ENT did surgery which has helped some. He also did allergy testing, to 19 allergens, and told me I was highly sensitive to all of them. He wants me to start allergy shots (immunotherapy), but I question whether I may be allergic to additional, untested allergens. I don't want to go through years of time commitment and expense and still find myself miserable because of untested and untreated allergies. My question, then - would an allergist test for and treat more allergens than the ENT surgeon did?

A. These positive tests are only important if they match your personal allergy medical history. This correlation has far greater importance than the number of tests done, which can vary based on one's history, geographic location, etc. For example, a positive skin test to ragweed pollen is only meaningful if you experience allergic nasal and eye symptoms during the ragweed pollen season in the late summer. A positive test to dust mites is only important if you experience sneezing or itchy eyes when you vacuum or disturb indoor house dust. People without identifiable allergic triggers could have non-allergic nasal conditions. If indeed you have symptoms that match your allergic sensitivities identified by skin testing, allergy injections may be useful in controlling chronic nasal symptoms and sometimes in preventing future sinus infections. Before going straight to allergy injections, however, we recommend that everyone have a good trial of medications known to be effective in controlling nasal allergy and preventing sinus infections - including nasal steroid sprays. Environmental control measures can also be helpful, depending on the allergen. Read more about the accurate diagnosis and treatment of environmental allergies.

Most allergy sufferers feel board-certified allergists are more effective at relieving their symptoms. In a study, 54% of sufferers reported their allergist recommended a treatment plan that was more effective than any other non-allergist (such as ENT surgeon, family physician, etc.), or over-the-counter medication. An allergist is an expert trained at taking a detailed medical history, and interpreting allergy test results, and is successful in treating up to 90 percent of patients with seasonal allergies and 70 to 80 percent with perennial allergies. Read more about the training received by a board certified allergist.

Q. My allergist has performed skin tests which have been of some help. Have you information on the various kinds of blood tests available for possible food allergies?

A. There are two kinds of food allergy blood test. One is IgE based and reflects the most common allergic reactions. One can choose each food to be tested, shrimp, salmon, orange, peanut, etc. Another type of food test measures IgG antibodies to foods. This is controversial with unclear clinical significance since people can have these type of positive tests without any clinical problem.

Q. If a person has a runny nose, bleary eyes and is sneezing during pollen season, how important is it to see an allergist? Does it matter what you're allergic to, specifically? And are allergy shots — immunotherapy — worth the time and trouble?

A. It's definitely helpful to understand what triggers your symptoms, especially if you're having difficulty controlling them with over-the-counter medications, having complications like sinus infections or asthma, or feeling so run down that it affects your ability to work or go to school. Symptoms can be hard to interpret, but a board-certified allergist has particular training and experience that help find answers.

A patient with allergic sensitivity to pollen, for example, may not have symptoms after a minor exposure. But with heavy exposure or other allergens added in like pet dander or dust mites, the person's allergy threshold may be exceeded and symptoms begin.

That's why some patients have symptoms mainly during pollen season, but they're not just allergic to pollen. They may also have allergies to things like pets and dust mites, and if those other allergens were reduced, the individuals might be able to tolerate more pollen exposure.

Regarding allergy shots, how helpful they could be depends on the severity of symptoms. Allergy shots are most effective for inhaled allergens such as pollen and other environmental allergens, animal dander, and mold spores. The shots help build tolerance to an allergen so that the patient can tolerate exposure. This tolerance continues even after the immunotherapy ends — most patients don't need allergy shots again.

For information on immunotherapy and allergy tests, listen to our "Ask the Allergist" podcast.

Q. How often should allergy testing be done?

A. Allergy testing should be done initially, and then when indicated. Indications may be:

  • A change in disease patterns
  • A decision that something was missed on the original tests
  • Probably when changing to different areas and different physicians
  • After 3-5 years of immunotherapy that has been successful, or
  • When making a decision about stopping immunotherapy.

Q. I recently underwent a scratch test to determine what I’m allergic to. The results of all 45 allergens they tested were negative (with the exception of the histamine control), although I clearly have seasonal allergies. Is it so important that I learn the cause of the allergies, or should I just go ahead with the treatment that works (a combination of antihistamine and nose spray)? Are there panels of less common allergens available for scratch tests?

A. There are over 50,000 species of mold in air. You were undoubtedly not tested for all of those. The same is true for pollens and other allergens. The skin testing that normally is done is for the most common things. Many things are less common or even unknown. If you were negative to the 45 allergens then you probably have either a sensitivity to something else that is less common or you have nonallergic rhinitis that just seems like an allergy.

At any rate, you certainly can get on with treatment. A combination of nasal sprays, antihistamines and eye drops (if needed) should help. If not, there are other options that don't require knowledge of what you are allergic to. Ask your doctor for advice.

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