Less common and 'emerging' food allergens

Aside from the 'Big 8' that require labelling in many countries around the world, a number of other foods that cause allergic reactions are the focus of scientific research. In this issue of eNews, we take a look at some of the investigations that have been published recently.

Rice

Rice is commonly thought to be 'hypoallergenic', with current dietary guidelines recommending it as one of a child's first solid foods. However an Australian study has revealed that rice can trigger a rare but severe allergic reaction in babies and toddlers. The condition, food protein-induced enterocolitis syndrome (FPIES), causes vomiting and diarrhoea and was thought to be brought on by milk and soy, and more rarely by vegetables, meats and grains.

The Children's Hospital at Westmead in Sydney have recently published their findings from a retrospective study of 56 reactions among 31 babies over a 16-year period. They found that about half of the cases of FPIES appear to be triggered by rice, with the symptoms more severe than those caused by cow's milk or soy proteins.

Four out of 10 children for whom rice was the trigger required resuscitation with intravenous fluids. This compares with one in six of those for whom cow's milk or soy proteins were the triggers. The authors warned paediatricians to be aware that rice could trigger severe reactions in a small number of susceptible children.

Reference: Sam Mehr et al 2008. Rice: a common and severe cause of food protein induced enterocolitis syndrome. Archives of Disease in Childhood. (online ahead of print).

Maize

Despite its wide consumption, maize has been described only recently as a cause of food allergy. Still, maize allergy is not very common, so it is perhaps not surprising that few studies have been conducted to investigate this allergy. A group of Italian scientists who believe this area is worthy of more research have found that maize does cause IgE-mediated allergic reactions in both adults and children. Indeed, nearly half of the subjects recruited for the study were confirmed by challenge tests to be allergic to maize. Furthermore, twenty-three percent of the positive challenge patients manifested symptoms that involved two organ systems, thus fulfilling the criteria for maize-induced anaphylaxis.

The authors concluded that maize can pose a risk for symptomatic food allergy at a dose of 100 mg.

Reference: Scibilia et al. 2008 Maize food allergy: a double-blind placebo-controlled study. Clinical and Experimental Allergy (online ahead of print)

Eggplant

Eggplant ranks twelfth among the leading vegetable crops of the world, and in India a relatively large number of individuals appear to experience food-related symptoms to eggplant. In order to determine the actual prevalence, a group of Indian scientists conducted a study of seven hundred and forty-one subjects (age range: 5–60 years) randomly selected from rural and urban areas of Mysore city.

The results showed 9.2% of the subjects experienced adverse reactions to the ingestion of eggplant, although the researchers proposed this was possibly due to the pharmacologic action of histamine and other non-protein components, rather than to specific protein allergen(s). The prevalence of IgE-mediated eggplant allergy was estimated at 0.8%, with higher rates of sensitization in females. Females were twice as likely to be sensitized as males. Female predominance (4:1) was found to be greater in the 16–30 year group.

Reference: Harish Babu et al. 2008 A cross-sectional study on the prevalence of food allergy to eggplant (Solanum melongena L.) reveals female predominance. Clinical and Experimental Allergy (online ahead of print)

Lentils

Legume allergy, mainly to lentils and chickpeas, is the fifth most common cause of food allergy in Spanish children. Martínez San Ireneo and his colleagues conducted a study on 54 children with clinical allergy to legumes to further investigate these allergies. They found that allergy to lentil was the most frequently diagnosed legume allergy (43 children [80%]), followed by allergy to chickpea (32 children [59%]). The majority of children (69%) had allergy to more than one legume. The most frequent symptoms of allergy were respiratory (rhinitis and/or asthma) and skin reactions.

The researchers further investigated cross-reactivity among lentils, chickpeas, peas, white beans and peanuts. This was evaluated by ELISA inhibition experiments and oral food challenges. The oral legume challenges demonstrated that the most frequent associations were allergy to lentils and chickpeas (57%), allergy to lentils and peas (54%) and allergy to lentils, chickpeas and peas (43%). The authors therefore concluded that there is a high degree of cross-reactivity among lentils, chickpeas and peas in Spanish children.

References:

Martínez San Ireneo et al 2008. Clinical features of legume allergy in children from a Mediterranean area. Annals of Allergy, Asthma and Immunology Vol 101(2) pp. 179-84.

Martínez San Ireneo et al 2008. In vitro and in vivo Cross-Reactivity Studies of Legume Allergy in a Mediterranean Population. International Archives of Allergy and Immunology. Vol147 pp. 222-230.