“I am allergic to all nuts.”
A friend of my wife cornered me at a Christmas party this year and told me her story. Hearing such tales is an occupational hazard for physicians, but I usually take it in good humor and sometimes even learn something myself. She told the story of living through an anaphylactic episode at age 13 after eating a single cashew. As she was chewing it a burning painful itching sensation began suddenly on her tongue and spread to the back of her throat. Next she started itching all over, turned red, felt nauseated and weak, and started to have trouble breathing due to her very tight throat. She was rushed to the emergency room where she had several shots, an iv was placed, and after awhile she felt better and was allowed to go home. Her pediatrician told her and her family at that time to never allow her to eat nuts again.
“Am I really allergic to all nuts?”
She had been wondering whether the advice she was given was true, and she certainly was interested in trying some nuts if it would be safe. Many holiday recipes use nuts to flavor or garnish a dish. Some Christmas cookie recipes use a base of ground up nuts instead of flour. Oriental foods often have peanut or cashews. Mediterranean diets also emphasize nuts as a source of healthy fats and protein.
Cross reactivity is a term used in allergy that describes the body’s ability to have recognition of a food or airborne allergen due to an allergy to a different food or airborne allergen. For example people who are allergic to hickory tree pollen are also allergic to pecan tree pollen due to the similarity of the pollen. People who are allergic to cow’s milk can also be allergic to goat’s milk in some cases. With nuts the case is trickier. Studies of peanut allergic patients have noticed that almost half of them develop allergies to tree nuts. However there seems to be no cross reactivity between tree nuts and peanuts so this represents the development of a new food allergy. However there is some cross reactivity among tree nut families so caution is warranted. We have some information on this through research that involves testing blood serum from tree nut allergic people against all tree nut proteins that are known. Other research involves giving tree nut allergic people oral food challenges with different nuts and observing them for reactions.
For more on this go to (http://foodallergies.about.com/od/nutallergies/p/treenutallergy.htm).
If you want to see some of the science of cross reactivity studies using double immunodiffusion go to http://treenuts.ca/nutallergy.pdf.
“Am I just nuts to do this?”
Seeing the allergy specialist was the right move for her. The new Food Allergy Guidelines certainly advises people with these types of questions to see a specialist for a discussion of testing options. My wife’s friend made an appointment to see me and I skin tested her to all the nuts. She had positives to cashew and pistachio which are known to be cross reactive. She was negative to another family of tree nuts (walnut and pecan). She underwent a food challenge in the office to both and did well. She decided to go ahead and eat these as she was reassured that the risk of reaction was very low. At last report she enjoyed both walnuts and pecans this Christmas season and was thrilled. She continues to avoid cashews, will not eat pistachios, and keeps her epinephrine injector in her purse just in case.
Tag Archive for 'food challenge'
“I am allergic to all nuts.”
This week a mother and her 5 year-old son visited me for an opinion on his food allergies. She brought with her a 20 page colorful and flashy printout of labs done a few weeks ago. The testing was quite comprehensive in evaluating antibody response to over 100 foods and 30 environmental allergens. It checked for the presence of other antibodies indicating possible celiac disease and also measured total antibody levels of various types. Many foods were identified as positives and most of them were her son’s favorites. She was in despair as she sought to provide him excellent nutrition, deal with his frustration at being denied some of his beloved foods, and try to make sense of the advice she was given by the nurse at the pediatric office. She had been simply told not to give him any of these foods until she could make an appointment with the allergist.
I asked her why the tests had been run. She stated that her son had had mild to moderate eczema for several years and recently had over a week of hives that led to the test being done. She had no idea he was so allergic to so many foods.
As I reviewed the tests with her it became clear to me that all of the positive tests were of the IgG4 type. These tests are not approved for the detection of allergic response by the body. The serum IgE tests were negative to all foods. Some of the environmental IgE tests were positive such as dust mite and cat dander. The celiac tests were negative as well. I was troubled at the use of testing methods that were not approved for allergy evaluation. I was also troubled by the misuse of such tests to alter diet and lifestyle unnecessarily. No testing was indicated at all by the history and therefore the financial cost and family turmoil could have been avoided.
The National Institute of Allergy and Infectious Disease (NIAID) released the first ever Guidelines for the Diagnosis and Management of Food Allergy last week (http://www.niaid.nih.gov/topics/foodallergy/clinical/Pages/default.aspx). The intent of the guideline is to assist clinicians in properly diagnosing and managing food allergy. The recommendations are based on studies and expert opinion both. They address both recommended and controversial methods of testing for allergy. It addresses dietary advice for both the allergy sufferer and family members. It addresses proper emergency management techniques and medications. Finally the guideline recommends that patients with suspected food allergy see a specialist who can look at all the facets of the problem: the history, the exam, and the testing results. Food challenges can sometimes also be helpful in understanding the relevance of skin or specific IgE blood testing. In early 2011 the NIAID will release a lay person version of the food allergy guidelines. We will post the link here when it is available.
After our lengthy conversation about the facts of food allergy and testing mother and son were excited to have his favorite foods restored to him. After reviewing the facts surrounding his rash we decided that his outbreak of hives was likely due to a cold virus he suffered around the same time. She called the office today to report that he is doing well, eating all his favorite foods, and enjoying being a normal boy again.