ALLERGY TESTING

 

Allergies are a major topic of conversation these days. Sometimes it’s very clear what is provoking symptoms, and sometimes it’s about as clear as mud. I wanted to shed some light on the subject, and here are several FAQs to help.

 

Q: Can you summarize for us what types of allergies are out there?

 

A: Typically there are 4 categories of allergies that we see often.

 

Environmental allergies – from grasses, pollens, etc are common seasonally, and sometimes year-round. Sufferers endure symptoms ranging from itchy watery eyes, runny noses, sneezing, to wheezing, hives and chronic congestion.

 

Food allergies – certainly a hot topic now. Sufferers typically may have hives, itching, nausea or vomiting, and in the worse case scenarios wheezing, swelling of the airway or anaphylaxis.

 

Venom allergies – we see these more often in the Spring and summer when bees and wasps and mosquitos are more prevalent. These reactions can range from intense local itching, to swelling of the bitten area, and in extreme cases, systemic reactions leading to anaphylaxis.

 

Lastly, contact allergies – these typically occur as rashes or skin eruptions associated with direct contact from metals, latex, occupational or environmental agents. Those affected have chronic itching, typically local, and these rarely progress to serious symptoms.

 

 

Q: What is the single most important thing to help your doctor make a diagnosis?

 

A: HISTORY HISTORY HISTORY. We ask many questions to get a complete understanding of the circumstances surrounding a reaction and possible causes. So bringing notes, photos or video to your visit, as well as food labels or packaging from suspected allergens can help us do the detective work together. When the answers are not crystal clear (as in the case with some food allergies) or if symptoms of environmental allergies can’t be well controlled with available medications or avoidance, then testing may be indicated.

  

 

Q: Let’s walk through them then. First, Hay Fever and environmental allergies.

How are they diagnosed and do we always need testing?

 

A: If an individual has a pattern of environmental allergies – like typical hay fever every spring, we have a few options. First we treat with available tools like non-sedating antihistamines, perhaps a nasal or eye allergy preparation, and other strategies to reduce pollen entering the home. Despite our best efforts if allergies are still difficult to control and interfere with quality of life then skin testing is done.

 

Small amounts of allergen representing the LOCAL grasses, trees, pollens, and animal danders etc are placed on the skin and pricked with a tiny needle. Those areas are observed for several minutes. A NEGATIVE test usually means you are not allergic – however a POSITIVE TEST may not be completely predictive of true allergy.

 

Depending on the severity of the skin prick test’s reaction, allergists may recommend another layer of allergy medications or even immunotherapy (allergy shots) – especially if these environmental allergens cause severe symptoms like severe asthma.

 

 babypatchtest.jpeg

 

 

Q: What about contact allergies?

 

A:  These are fairly common. I saw many kids in my practice with local areas of itch and redness, typically at the wrist, belly button area, earlobes or the back of the neck. My son had rashes beneath each of the snaps of his infant pajamas. The culprit – Nickel - an inexpensive metal used in watch casings, earrings, jewelry, snaps and belt buckles. Direct contact with skin causes a very itchy uncomfortable rash that doesn’t go away unless the offender is removed. But if the rash’s source is in question, we can do Patch Testing. This is typically done also when babies have “mystery rashes” and working folks have rashes on hands or skin that may be related to contact with a workplace allergen.

 

 

Based on history, small amounts of suspect allergens are placed on the skin, and covered with an occlusive bandage for 48 -96 hours. The bandages are removed and those areas are examined for redness and inflammation. If there is redness, you have a contact allergy. Typically treatment involves avoidance of the offending agent moving forward and the rashes will resolve on their own, or with a topical steroids.

 

 

Q: And food allergies – we hear about so many tests. How do we know for sure?

 

A: If there is a reproducible reaction each and every time a food is eaten, it’s easy to implicate that food as the culprit. When the diagnosis is crystal clear by history, your doctor will educate you about avoidance and develop an allergy action plan for your child for home, daycare or school. This may or may not include an epinephrine auto-injector depending on the severity of symptoms.

 

However, if a child has had a reaction that is unclear, or the history fails to reveal the cause then testing may be indicated. In addition, if a child has a significant allergy to a peanut (a legume) or a tree nut, more testing needs to be done as there are several proteins that peanuts and treenuts have in common, placing a child at risk for other nut allergies.

 

Skin prick testing is typically done looking at the suspect allergens a week or 2 after the event (as the body needs time to restore it’s source of IgE – that immune chemical we make in larger amounts that helps trigger a positive skin test but gets depleted after an allergic reaction). Patients are asked to NOT take antihistamines so that the sensitivity of the test is greater. If there is a significant reaction to a specific allergen your allergist may then recommend a direct food challenge in his/her office to verify if that food truly is your enemy. This is the gold standard of testing for food allergies. That said, if you have had a history of anaphylaxis to an allergen, with a positive skin prick test, you and your allergist may elect to not have a food challenge, as this may be risky for you.

 

Q: What about blood tests for food allergies?

 

A: If a patient has a skin condition where skin testing isn’t reliable, or is taking medication that interferes with skinprick testing, or in the case of kids who may not tolerate the pricks, then specific IGE blood tests are done. The lab adds the suspected allergen to your blood sample and then measures the amount of antibodies your blood produces to attack the allergens. It’s not a good screening test due to high false positive results. If there is a significant elevation of IgE against a food, your doctor will likely recommend a direct food challenge in the office to verify or not.

 

Q: Are there any tests out there we shouldn’t have?

A:  Measurements for allergen(food)-specific IgG are often performed by alternative health practitioners in the context of food allergies. It is normal to have specific IgG to individual foods, because a patient has eaten them, so testing will yield multiple positive results. This test does not predict food hypersensitivity or allergy.

 

Other types of testing not validated by good science include kinesiology, cytotoxic tests, electrodermal testing and provocation/neutralization tests. They result in unnecessary testing, and inappropriate advice.

 

 

Q: Insect stings?

 

A: It’s very common for kids and adults to have local, sometimes impressive reactions to mosquito, bee and wasp stings. However, if there are systemic reactions like hives, wheezing, or anaphylaxis, your allergist likely will prescribe an epinephrine auto injector. Immunotherapy (allergy shots) may be prescribed under these circumstances. This would only be for bee or wasps – fortunately mosquito reactions, although impressive, rarely lead to dangerous consequences.

 

 

Q: Last thoughts?

 

A: There is no single test out there that predicts the severity of an allergic reaction. And as is the case, especially with food allergies, reactions can vary from incident to incident. So if your healthcare provider encourages you to have an epinephrine auto-injector nearby at all times, take that piece of advice seriously. Stick with your allergy action plan, and if it fails you, re-visit your plan with your healthcare provider or allergist!


For a clip of the episode on Home & Family go to: https://youtu.be/dAEp9vRqxM0