Thank you for your inquiry.
I will answer each of your questions in the order that they were asked.
1. Is skin testing or blood testing preferred for suspected avocado allergy in an infant?
I do not believe either are preferred. In this situation, I would do both.
2. Should associated foods such as bananas, kiwis be tested?
In my opinion, yes. Avocado has a broad cross-reactivity with many other foods, and you would get a better idea of her atopic state. Of course, as you know, a positive skin test does not necessarily mean that the child cannot eat the food. It simply implies sensitivity.
3. Is there an optimal age for testing an infant? Any benefit in waiting until she’s older?
Infants can be tested at almost any age, and testing is based more on the nature of the problem rather than on the age of the child. In this instance, testing at least to avocado is indicated. You may get disagreement between allergists as to how extensive testing should be at this point, and this is a question open to debate. But in general, one does not use an age to determine when to skin test. One tests according to the nature of the problem and its severity. I would see no benefit in waiting until she is older at least to test her to avocado and, as noted, I would test to cross-reacting foods. However, testing to related foods would be open to opinion.
4. Is latex-fruit syndrome a concern in the future?
Avocado is strongly cross-reactive with latex, and in one study of latex-allergic individuals, 53% showed allergen-specific IgE-antibody to avocado. It had the highest incidence of cross-reactivity of any of the foods tested which included potato, banana, tomato, chestnut, and kiwi (1).
One of the major allergens in avocado is a Class I chitinase. This is a panallergen and is associated with extensive cross-reactivity with a number of foods from different families. This Class I cross-reacts with a major latex allergen, hevein (2).
So, clearly there is distinct cross-reactivity between avocado and latex. This would make this child subject to latex sensitivity. However, these data are taken from studies in patients known to be allergic to latex and who are also exposed to avocado. Your child starts with a presumed allergy to avocado, but if she is not exposed to latex, obviously she would not be at risk for the latex-fruit syndrome. Nonetheless, if she is exposed to latex, she is at highly increased risk.
In summary, I would test using both skin and blood tests. In my opinion, there is no “optimal” age for skin testing. Indication for testing is based on the history more than the age of a child in most instances. Whether to test with related fruits is controversial, but I personally would strongly consider doing this. Finally, there is marked cross-reactivity between avocado and latex, but data regarding the latex-fruit syndrome in regards to avocado are all taken from studies in patients known to be allergic to latex. Although your patient is at increased risk, unless she is exposed to latex to become sensitized, she would not develop latex-fruit syndrome.
Thank you again for your inquiry and we hope this response is helpful to you.
1. Beezhold DH, et al. Latex allergy can induce clinical reactions to specific foods. Clin Exp Allergy 1996; 26(4):416-422.
2. Diaz-Perales A, et al. Cross-reactions in the latex-fruit syndrome: a relevant role of chitinases but not of complex asparagine-linked glycans. J Allergy Clin Immunol 1999 (September); 104(3 Pt 1):681-687.
Phil Lieberman, M.D.
I wanted to give you a follow-up on my reply to your question regarding the 6 month old girl who developed urticaria after eating avocados. In response to one of your questions, I stated that data regarding the cross-reactivity of latex and avocados are taken mainly from studies evaluating patients with known latex sensitivity to assess whether or not they have cross-reactivity with foods. Since responding to you, we have answered a question posed by an anesthesiologist regarding the risk of patients with pollen-fruit syndrome undergoing surgery in regards to their potential to react to latex (even in the absence of a previous history of latex allergy).
I asked Dr. Kevin Kelly, who is a nationally known expert in latex sensitivity, to respond to the anesthesiologist's question. Dr. Kelly's response indicates that there may be a greater risk than my perception as expressed in my original answer to you. I am therefore copying the inquiry from the anesthesiologist along with Dr. Kelly's response below to update this information for you as well as have it posted along with your inquiry on our website for our readers.
Thank you again for your inquiry.
Phil Lieberman, M.D.