Cashew has recently become widely available in the form of butter spreads. Cashew causes symptoms in formal food challenges (1) and has caused death (2). A report found 0.08% of British 4-year-olds to be allergic to cashew (3), and 40% of 142 French peanut-allergic subjects were found to be sensitized to cashew (4). We report here the clinical features of cashew allergy in 29 paediatric and adult subjects whose history of reaction was supported by a positive skin prick test to cashew or a raised serum level of cashew-specific IgE. Two subjects had positive open challenges to cashew. This study was approved by the Southampton Joint Ethics Subcommittee.
The age range of the 29 subjects was 1–30 years (median 7.5 years). Nineteen (65%) of the subjects were female. Twenty-six (89%) subjects were children (under 16 years). The median age of onset was 49 months (range 2 months–27 years), and 96% of subjects had not knowingly been exposed to cashew before the exposure causing the first reaction. Fourteen subjects (48%) reacted to minimal contact with cashew; that is, smelling, touching, or tasting, but not eating, cashew. No one reported more than four reactions. Twenty-one subjects (72%) had suffered only one reaction to cashew, five (17%) had suffered two reactions, and only three had experienced more than two reactions. Fourteen subjects (48%) reported wheeze after first exposure, and 11 (38%) reported collapse or feeling faint.
This series describes features of nonfatal reactions to cashew. These features include the severity of cashew allergy (at least equal to that of peanut allergy), the importance of which is counterbalanced by the relative rarity of accidental exposure to cashew, compared to peanut (1, 5), and the later age of onset of cashew allergy (5, 6).
The young age of onset of peanut allergy has been attributed to the availability and convenience of peanut butter as a spread. By anecdotal evidence, parents have started to avoid peanut butter, in line with UK government advice, especially if there is a positive family history of allergy. We have seen cashew-allergic families who had been avoiding peanut butter and started using cashew butter instead, unaware of the potential for reactions of at least equivalent severity to peanut-allergic reactions. Cashew butter is now widely available in the UK, and it is reasonable to speculate that a decrease in age of onset of cashew allergy may become evident over time.
Allergists and other physicians must be aware that although cashew avoidance is easier than peanut avoidance, cashew allergy represents a threat to life that is at least as severe as that posed to peanut- or tree-nut-allergic subjects by the respective allergenic foods.