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With kiwifruit becoming ubiquitous in grocery stores worldwide, reports of allergic reactions to the fruit have also increased. But some varieties may be less likely than others to trigger allergies, a small study suggests.
In tests of 37 adults with kiwi allergies, researchers found that certain cultivars of the fruit -including the "gold" variety- tended to be less allergenic than the common deep-green variety known as Hayward.
The findings, reported in the Journal of Allergy and Clinical Immunology, raise the possibility that people who avoid kiwi because of allergies might be able to reintroduce the fruit into their diets.
The kiwifruit, native to southern China, was once considered an "exotic" fruit, but since the 1970s its availability and popularity has increased worldwide. With wider consumption has come an increase in incidents of allergic reactions to kiwi.
Kiwi source of food allergy
In Sweden, Finland and France, kiwi has become one of the top-10 sources of food allergies, noted Dr Karin Hoffmann-Sommergruber from the Medical University of Vienna.
In the current study, Hoffmann-Sommergruber and her colleagues looked at whether different kinds of kiwi vary in their tendency to provoke immune system reactions and symptoms in people allergic to the fruit.
They assessed six kiwi varieties, including Hayward, the most commonly available cultivar, with the familiar medium-brown skin and bright-green flesh, and summer 3373, a variety in the same kiwi "species" as Hayward but with light-green flesh.
The other tested kiwifruits included Hort 16A, marketed as "Zespri Gold" and the most widely available golden-fleshed variety; Jintao, a golden variety newer to the market; and two varieties of a species called Eriantha expected to come to market in the next 10 to 20 years; they are smaller and lighter-skinned than other kiwi varieties and have deep-green flesh.
Hayward kiwi most allergenic
In general, the Hayward kiwi triggered the most significant skin reactions, while the lighter-green summer and gold Hort 16A varieties led to the mildest reactions.
A subgroup of participants took food-challenge tests. Again, the Hayward kiwi appeared the most allergenic. Two of 11 subjects had severe reactions to this variety. Of the rest, most had moderate symptoms, like abdominal pain and diarrhoea, and two had no symptoms.
Two of three food-challenge participants given the summer variety had mild oral reactions and one had oral symptoms and a skin rash. Of eight participants given the gold Hort variety, two had no symptoms, and the rest had mild or moderate ones.
Neither the summer nor the Hort varieties triggered a severe reaction in any subject.
Allergens varies among kiwi
Research had indicated that the allergenicity of the major kiwi species varies, Hoffmann-Sommergruber said.
In general, the concentration of the major allergy-triggering protein in kiwi is 50 times in green kiwifruit compared with golden kiwi, she added.
The current findings, according to Hoffmann-Sommergruber and her colleagues, may help sort out which specific kiwi varieties can be safely tolerated by the allergy-prone. But, they say, further research in large groups of patients is still necessary.
The worldwide prevalence of kiwi allergy is not clear. People with pollen allergies are more likely to react to kiwi (as is true of a number of other fruits). People with latex allergies also have a higher risk of kiwi allergy due to similarities in the allergy-triggering proteins found in latex and kiwi.
(Reuters Health, Amy Norton, December 2010)
