Crossreactions between foods

Cross-reactivity is due to a reaction to identical or similar protein allergens that occur in more than one food, or in a food and an inhalant pollen. This is different from associated reactivity where two or more food allergens may be seen to be associated epidemiologically. A good example of the latter is the high rate of association between egg and peanut allergy although the allergens are not related. Establishing a cross-reaction requires the demonstration of at least a positive correlation between the magnitude of specific IgE to both foods, and RAST inhibition studies are needed for confirmation. Cross-reactivity is seen at an immunological level when a subject is sensitised to both foods on the basis of positive skinprick or specific IgE testing to both foods. However, often only a smaller proportion will demonstrate clinical cross-reactivity, that is a reaction to both foods on clinical exposure.

Table 10.13 lists the common cross-reactions involving foods. For fish and legumes, there are good data regarding cross-reactivity at immunological (skin prick/specific IgE) and clinical levels. One study demonstrated 73% immuno-logical cross-reactivity for ten different fish species, but only 28% clinical cross-reactivity to two or more of the same ten species (Bernhisel-Broadbent et al. 1992). In the case of legumes, the same authors demonstrated immunological

Table 10.13 Common cross-reactions involving foods

Index food or

Cows' milk

Chicken egg

Cod

Shrimp

Peanut

Latex

pollen

Cross-reacting

S°y

Duck, geese &

Other fish

Crustaceans,

Other legumes

Fruits and

foods

11-35% clinical cross-

turkey egg

28% clinical

molluscs

e.g. soya bean,

vegetables

reaction

cross-reaction

garden pea, chick

e.g. banana, pear,

Sheep and goat milk

73% skinprick/

pea, lentil, guar,

avocado, chestnut,

50-75% clinical cross-

IgE cross-reaction

liquorice, carob,

papaya, potato,

reaction

gum arabic and

tomato

other beans

5-60% clinical

cross-reaction

75% skinprick/

IgE cross-reaction

References

Juntunen and Ali-Yrkko

Langeland 1983

Bernhisel-

Musmand et al.

Bernhisel-

Lavaud et al. 1992

1983

Broadbent et al.

1993

Broadbent and

Beezold et al. 1996

Bardare et al. 1988

1992

Sampson 1989

Zeiger et al. 1999

Crespo et al. 1995

Index food or pollen

Birch pollen

Ragweed pollen

Mugwort pollen

Grass pollen

Cross-reacting foods

References

Fruits and vegetables e.g. apple, celery, carrot, potato, kiwi, hazelnut, cherry

5-60% clinical cross-reaction

10-75% skinprick/IgE cross-reaction Dreborg and Foucard 1983 Foucard 1991 Caballero et al. 1994

Fruits and vegetables e.g. watermelon, melon, cucumber, banana

Ortolani etal. 1998

Legumes (see peanut)

Also celery, carrot, nuts, mustard

Caballero and Martin-Esteban 1998

Tomato, potato, green pea, peanut, watermelon, melon, apple, orange, kiwi

Caballero and Martin-Esteban 1998

cross-reactivity between legumes in 49 out of 69 patients (71%) with atopic eczema, but only 2 out of 41 patients (5%) evaluated showed clinical cross-reactivity (Berhisel-Broadbent and Sampson 1989). By way of contrast, another study showed considerable clinical cross-reactivity between the legumes in the context of acute reactions (Crespo et al. 1995). In the latter study, out of 67 patients seen in an allergy clinic, 43 (64%) showed clinical allergic reactions to more than one legume (mainly lentil, peanut, chick pea, pea and bean).

In Scandanavian countries there is a high prevalence of birch pollen sensitisation, reaching up to 10-15% in teenagers and young adults (Eriksson 1978). Between 30% and 75% report clinical reactivity to fruits and vegetables, occurring chiefly as the oral allergy syndrome in adolescents and adults, with apple being the food most commonly implicated (Dreborg and Foucard 1983, Pastorella et al. 1995). Clinical cross-reactivity can be confirmed in around 6075% of birch pollen allergic patients with immunological cross-reactivity to foods (Foucard 1991). These data are from patient history and food challenges done at home, and a lower reaction rate is likely with more rigorous food challenge procedures (Caballero et al. 1994).

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