Ask The Expert
January 12, 2021
Peanuts and Anaphylaxis Due to Cashew Nut
Recently I saw a one year-old child with a history of well-controlled eczema with anaphylaxis to cashew nut. His SPT was 13 mm wheal to pistachio (cashew was unavailable) and his specific IgE was 7.44 to both cashew and pistachio. He has never been introduced to peanut. His SPT to peanut was 4 mm (PC Histamine was 9 mm). His specific IgE is unavailable but ordered. His mother is wondering if it is safe to feed peanut butter with his history especially without prior exposure. My current recommendation was to definitely avoid all tree nuts (here is another twist – he can tolerate almond milk) and peanuts due to the potential of developing reactivity to peanuts; however, I also read that he most likely will be able tolerate peanuts.
From the Editors: The clinical management of patients with one or two known tree nut allergies who have never ingested peanuts or another tree nut is a problem faced by most allergists on a weekly basis. Read what our experts recommend.
Answered By: Crhistian Toribio, MD
Although in vitro cross-reactivity between peanuts and tree nuts is high (86%), as well as tree nut sensitization in patients with peanut allergy (87%), clinical co-allergy is prevalent lower. Self-reported studies estimate 20% - 60% prevalence, while Oral food challenge (OFC) studies report even lower (4% - 40%)1,2. Therefore, deciding which patient has to avoid a specific tree nut or peanut is sometimes challenging.
There is evidence of cashew allergy based on SPT and sIgE and a high probability of pistachio allergy in this patient. However, the avoidance of other nuts if a patient is allergic to one is changing. Some factors could increase pistachio allergy risk in patients with cashew allergy, such as low reaction dose to cashew3. Consequently, some authors now recommend performing an OFC to pistachio in those with cashew allergy regardless of SPT or sIgE level to prevent unnecessary pistachio avoidance, especially if parents want to introduce it to their children's diet. A discussion of the pros and cons of OFC vs. food avoidance with the family is also encouraged.
On the other hand, there is limited data about peanut avoidance by patients with a tree nut allergy (not a strong recommendation). LEAP trial showed an early introduction of peanuts in high-risk patients (e.g., severe eczema) could prevent the development of other food allergies. Guidelines vary from different countries; some recommend pre-screening using SPT, sIgE, or component-resolved diagnostic before peanut introduction4-6. Based on this, it is important to discuss with the family if they want to introduce peanut, the necessity of pre-screening (considering local guidelines), and peanut in-office challenge or home monitorization.
1. Couch C, Franxman T, Greenhawt M. Characteristics of tree nut challenges in tree nut allergic and tree nut sensitized individuals. Ann Allergy Asthma Immunol. 2017;118(5):591-6.e3.
2. Sasaki M, Koplin JJ, Dharmage SC, Field MJ, Sawyer SM, McWilliam V, et al. Prevalence of clinic-defined food allergy in early adolescence: The SchoolNuts study J Allergy Clin Immunol. 2018;141(1):391-8.e4.
3. Saba L, Clerc-Urmès I, Delahaye C, Chevillot E, Jarlot-Chevaux S, Dumond P, et al. Predictive factors of allergy to pistachio in children allergic to cashew nut. Pediatr Allergy Immunol. 2020;31(5):506-14.
4. Togias A, Cooper SF, Acebal ML, Assa'ad A, Baker Jr JR, Beck LA, et al. Addendum Guidelines for the Prevention of Peanut Allergy in the United States: Report of the National Institute of Allergy and Infectious Diseases-Sponsored Expert Panel. J Pediatr Nurs. 2017;32:91-8.
5. Joshi PA, Smith J, Vale S, Campbell DE. The Australasian Society of Clinical Immunology and Allergy infant feeding for allergy prevention guidelines. Med J Aust. 2019;210(2):89-93.
6. Schroer B, Bjelac J. Moving past "Avoid All Nuts": Individualizing management of children with peanut/tree nut allergies. Immunol Allergy Clin North Am. 2019;39(4):495-506.
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