Crossreactions involving plant allergens

Allergenic components of a novel food, Micronesian nut Nangai (Canarium indicum), shows IgE cross-reactivity in pollen allergic patients

BACKGROUND

New foods may present a risk for food hypersensitive patients. Several examples exist of allergic reactions caused by cross-reactive plant-derived foods, and new foods should be scrutinised before introducing them to the market. We have evaluated the clinical and serological relevance of cross-reactivity between Nangai and pollen allergens.

METHODS

Cross-reactivity was examined with Maxisorp RAST (radioallergosorbent test), RAST inhibition and Western blot, using sera from patients allergic to grass, birch and mugwort pollen. None of the patients reported having seen or eaten Nangai previously. To determine the biological and clinical relevance of the cross-reactivity, histamine release (HR) test, skin prick test (SPT) and food challenge were used.

RESULTS

There was prevalence for reactivity against Nangai in the group of pollen allergic patients. This cross-reactivity seems to be related--at least in part--to carbohydrate epitopes. Three out of 12 patients tested with Nangai were positive upon open challenge, but using double blind placebo controlled food challenge (DBPCFC) this could not be confirmed in two patients. The biological effects of Nangai on allergic patients were confirmed using HR and SPT.

CONCLUSION

The Nangai specific IgE found among pollen allergic patients addresses the need for control of new or changed foods before introduction to the market.

IgE-mediated food allergy--extensive review of the literature

Adverse reactions to food, i.e. food allergy and intolerance have gained considerable attention. This overview focuses on the diagnosis and management of IgE-mediated food allergy that is believed to be responsible for most immediate-type food-induced hypersensitivity reactions. Clinically, these reactions are characterised by a variety of signs and symptoms that occur within minutes or hours after consumption of the offending food. Reactions may be limited or more generalised with involvement of the skin, nose, eyes, and/or lungs. In more severe cases, cardiovascular symptoms including hypotension, shock, cardiac dysrhythmias and death can occur. In food-allergic individuals, IgE is produced against naturally occurring food components, primarily glycoproteins that usually retain their allergenicity after heating and/or proteolysis. While adults tend to be allergic to fish, crustaceans, peanuts and tree nuts, children tend to be allergic to cow's milk, egg white, wheat and soy more frequently. "Emerging" food allergens include tropical fruits, sesame seeds, psyllium, spices and condiments. These allergies frequently represent a cross-allergy to an allergen derived from another source, e.g. pollens or natural rubber latex. The evaluation of IgE-mediated food allergy relies on a careful history, physical examination, appropriate skin testing or in vitro testing with food extracts, and/or double blind, placebo-controlled food challenges. Avoidance remains the mainstay of therapy. However, allergens may be "hidden" and labelling can be non-precise or misleading, thereby severely hampering prevention. Patients with severe allergies should keep at hand an emergency kit with adrenaline, an antihistamine and an injectable rapid onset-of-action corticosteroid. At present there is no evidence to support the use of immunotherapy, except for research purposes. Production of "hypoallergenic" food is hampered by incomplete methods for assessing the allergenic potential of such novel foods.

Allergic sensitization and clinical reactions to latex, food and pollen in adult patients

BACKGROUND

Many latex-allergic patients are sensitized to one or more foods. Patients allergic to tree and/or grass pollens are also often sensitized to plant-derived foods. Atopy, defined in most studies as sensitivity to an aeroallergen, is a risk factor for latex allergy. The relative importance of pollen sensitivity, a sign of atopy, as a risk factor for food allergy in latex-allergic patients has not, however, been examined.

OBJECTIVE

To investigate the relationship between pollen sensitivity and sensitivity to food in latex-allergic patients.

METHODS

Forty-four latex-allergic patients (Groups 1 and 2), 24 of whom were also allergic to tree and/or grass pollen (Group 1) and 25 pollinosis patients who were not allergic to latex (Group 3) were studied. We obtained a history of reactions to food and skin tested them with 12 fresh-frozen fruits.

RESULTS

All 12 foods induced a skin test reaction in at least one patient in each of the three Groups. There were, however, twice as many positive skin test reactions to food in patients with pollinosis, whether or not they were allergic to latex, as there were in patients allergic to latex but not to pollen. Latex-allergic patients were most likely to have a positive skin test and a history of a reaction to avocado or banana whereas patients with pollinosis only were most likely to have a positive skin test and a history of a reaction to apple, peach or celery.

CONCLUSIONS

These results suggest that concomitant allergy to pollen is an important risk factor in determining which plant-derived foods sensitize latex-allergic patients.