Also known as the 'Chinese gooseberry', kiwifruit was once something of a rare delicacy, but according to a new study due to be published in the Journal of Allergy and Clinical Immunology, a worldwide increase in its consumption since the 1970s has led to a related upsurge in allergy-related cases, from "mild oral symptoms" characterised by rashes and mouth inflammation to "severe systemic reactions".
The new study , "Differences in the allergenicity of six different kiwifruit cultivars analysed by prick-to-prick testing, open food challenges, and ELISA", monitored 37 adults with kiwi allergies.
Hope for allergy sufferers?
Researchers found that cultivars such as the deep green or ‘Hayward’ variety are more allergenic that other varieties such as ‘gold’ kiwis, one possible implication of which is that sufferers from kiwi allergies may be able to selectively introduce other kiwi cultivars into their diets.
The academics examined immune reactions prompted by six kiwi varieties amongst study participants, including the most widely sold 'common green' cultivar Hayward and the slightly less common but also well-known Zespri Gold or Hort 16A, a golden variety.
Other fruits tested were the “more recently introduced” Jinatao and Summer 3373 varieties, while two smaller varieties from the Erianthan species were tested since they are “likely to become available on the market in future”.
The study participants were 26 Dutch and 11 Swiss outpatients recruited from the University Medical Centre in Zurich and University Hospital Zurich, with a mean age of just over 30, of whom 86 per cent were female.
The principal allergy determinant for the study – used on all 37 subjects – was a 'prick to prick' (PTP) skin testing process whereby a needle was inserted into various fruits to extract their pulp, which was then inserted in beneath the subjects’ skin in doses rising incrementally from 2g-50g to measure allergic reactions.
The researchers found that the Hayward and Eriantha varieties triggered the most marked reactions on skin (upon the basis of a PPT/histamine scale) while Hort 16A and Summer 3373 were responsible for the mildest allergenicity.
Meanwhile, 11 of the 37 participants also took ‘food challenge’ tests supervised by doctors, during which they were gradually given small amounts of the Summer, Hayward and Hort varieties.
Notably, severe reactions from 2 of the 11 subjects included respiratory problems and cardiovascular symptoms, with the Hayward kiwi again the most allergenic. Diarrhea and abdominal marked more moderate symptoms, while two participants displayed no symptoms.
Larger scale trials needed
The researchers stressed that the study was breaking new ground given the lack of existing research amongst humans: "So far, the allergenicity of kiwifruit cultivars has mainly been investigated in vitro. This study suggests there may be in vivo differences in allergenicity between the common green kiwifruit cultivar and other newly available kiwifruit cultivars."
Nonetheless, they urged caution in extrapolating from the study's limited scale, stressing that further research amongst a wider patient population was needed.Furthermore, "Differences in allergenicity of kiwifruit cultivars have to be interpreted with some caution, taking the individual patients’ reactivity toward cultivars into account."
Published online ahead of print: Journal of Allergy and Clinical Immunology,doi:10.1016/j.jaci.2010.10.003
"Differences in the allergenicity of six different kiwifruit cultivars analysed by prick-to-prick testing, open food challenges, and ELISA"
Authors: T-M. Le, P.Fritsche, M. Bublin, C.Oberhuber, S.Bulley, E. van Hoffen, B.K Ballmer-Weber, A.C. Knulst, K. Hoffmann-Sommergruber