Food allergy as a clinical entity has been known for much longer than allergy to natural rubber latex (referred hereto as latex). Latex-allergy (immediate type) is a recently discovered disease, its history is less than 20 years old. The overall prevalence of food
allergies is currently about 1-2% in western world populations1 while the prevalence of latex allergy in the general population appears to be clearly lower; figures in the range of 0.1% and 0.4%2 have been published. However, in atopic subjects, i.e. subjects capable of producing high amounts of IgE class antibodies (which
mediate the allergic reactions), latex-allergy prevalence has been reported to be around 1%. For centuries people have been exposed to pollens and innumerable foods derived from the plant kingdom. Perhaps the natural rubber latex from the Hevea brasiliensis tree should therefore be considered as just "another tree", a recent member of the long list of allergenic plants.
Of more interest is the question "when allergy to latex and foods is found simultaneously in a given patient, which one came first?" Currently, there is little solid evidence to support either option. Cosensitization is a possibility, i.e. the patient has become allergic to both latex and foods and these two phenomena need not be linked. However, banana-allergy is astonishingly common in latex-allergic patients; according to published reports about half of latex-allergic patients has experienced symptoms after eating bananas or avocados3,4,5. Studies on patients known to have fruit-allergy but no symptoms of latex allergy have not yet been published.
The meaning of allergen cross-reactivity is usually defined as follows; one may develop clinical allergy (or to develop IgE antibodies) to substances to which he/she has not been exposed. The basis for this phenomenon appears to be in structural similarity of the target molecules (sometimes seemingly very different and taxonomically unrelated) to which these IgE antibodies bind. However, little exact knowledge of such cross-reacting molecules is available. Several studies have been published dealing with possible cross-reactivity between latex and various food allergens, including such examples as avocado, kiwi and chestnut; pear, watermelon, pineapple, peach and papaya; and more recently, potato and tomato, of which all suggest they cross-react with latex2.
Latex-allergy is typically an occupational problem among glove-wearing healthcare workers, and is relatively rare in children except in the spina bifida or multi-surgery population. Yet, small children are exposed to latex proteins in teats and bottle nipples on a regular basis. Children frequently have allergies to various foods, in particular cow's milk, eggs, fish, peanuts and soy, while the spectrum of adult food allergies is different (dominated by celery, fish, nuts, peanuts and shrimps). Adults are often sensitive to
various pollens. Against this background the recent findings of Dr. Ylitalo and coworkers in Tampere, Finland which show children with latex-allergy frequently react also to banana, avocado and kiwifruit, are of considerable interest. The situation thus resembles
that in adults6.
In a case of obvious cross-reactivity, purified allergens from both latex and the fruits are required to compare the binding strength (affinity) of the patient's IgE to both candidate molecules, to determine which came first. Currently no published reports of such
studies are available. Fragmentary data can, however, be found in the literature4 indicating that, at least in adults, IgE binding to latex proteins usually appears to be stronger than to food allergens7. Furthermore, food extracts have been able to induce only partial inhibition of the binding of IgE from latex-allergic patients to latex proteins while latex proteins under these circumstances can bring about a 100% inhibition. This supports the contention that at least in adults, fruit allergy could be secondary to
latex allergy.
In summary, no final answers can be offered today but researchers continue to investigate this puzzling phenomenon.
REFERENCES
- Sampson HA: Food Allergy, Allergy and Allergic Diseases, 1517-1549, 1997
- Turjanmaa K, Alenius H, Makinen-Kiljunen S, Reunala T, Palosuo T: Natural rubber latex allergy (review). Allergy 51: 593-602, 1996
- Makinen-Kiljunen S: Banana allergy in patients with an immediate type hypersensitivity to latex. Characterization of cross-reacting antibodies and allergens. J Allergy Clin. Immunol 93: 990-6, 1994
- Alenius H, Makinen-Kiljunen S, Ahlroth M, Turjanmaa K, Reunala T, Palosuo T: Cross-reactivity between allergens in natural rubber latex and banana studied by immunoblot and immunoblot inhibition methods. Clin Exp Allergy 26: 341-348, 1996.
- Ahlroth M, Alenius H, Turjanmaa K, Makinen-Kiljunen S, Reumala T & Palosuo T: Cross-reactivity between natural rubber latex and avocado. J Allergy Clin Immunol 96: 167-173, 1995.
- Ylitalo L, Turjanmaa K, Palosuo T, Reunala T: Natural rubber latex allergy in non-operated and multioperated children. J Allergy Clin Immunol 1997 (in press).
- Alenius H, Mikkola 1 Reunala T, Turjanmaa K, Palosuo T. Unpublished observations, 1997.
