Recently I had to reevaluate 17 y/o high school student who wants to enroll in ROTC program at college. He has been one of my patients for allergic rhinoconjunctivitis due to tree, grass and ragweed pollens since 1999. In 2007 he developed a reaction including throat swelling after eating cherries. RAST confirmed cherry allergy. AS RAST was also positive to peach, avoidance of all plum group and EpiPen were recommended. Later he also developed a mildder throat discomfort due to pecan. Allergy skin test was positive to almond, pecan, hazelnut and walnut in 2010. Avoidance of all tree nuts was recommended.

I reviewed "Ask the Expert" from 08/27/12, 07/23/12, 6/14/11 and 10/1/10 but I still have some questions.

1). If RAST is negative or borderline positive, do you recommend oral challenge?
2). Although many people do not outgrow tree nut allergy, one article from 2005 indicated 9% may outgrow. Is it wise to oral challenge with pecan? If so, what to do with hazelnut, almond and especially walnut due to cross reactivity?


Thank you for your inquiry.

Your questions are certainly pertinent and germane. They deal with an issue that all allergists face on a relatively frequent basis. Unfortunately, however, there is no definitive answer to these questions, and I feel that you may get a variety of answers from different capable allergists-immunologists.

The issue as to whether to do an oral challenge is dependent on many factors, and in the final analysis, that decision is one that is made on the basis of the risk/benefit ratio, the desire of the patient to eat the food in question, and the potential to avoid the food without difficulty.

As far as the foods that you have mentioned (pit fruits and tree nuts), obviously none of these are essential elements of the patient’s diet, and all can be avoided without unreasonable difficulty. In addition, cross-reactivity between these groups is not sufficient to allow you to introduce all members on the basis of a test to one member of the class. Thus, in order to “clear” each fruit and tree nut, one would have to test to each.

For these reasons, I would not normally perform oral challenges to these agents unless the patient was insistent on such a challenge because of a desire to eat the food in question. I would be more likely, however, if the patient desired to eat a pit fruit, to do the challenge to a member of this group rather than a tree nut. However, again, I would make it clear to the patient that the only food in these groups that could be eaten safely would be the one(s) to which the challenge was/were performed.

Thank you again for your inquiry and we hope this response is helpful to you.

Phil Lieberman, M.D.

Close-up of pine tree branches in Winter Close-up of pine tree branches in Winter