Downloaded from https://www.cambridge.org/core British Journal of Nutrition (2006), 96, Suppl. 2, S95–S102 DOI: 10.1017/BJN20061869 q The Authors 2006 Food allergy: nuts and tree nuts . IP address: 1 2 1 1 Jesus F. Crespo *, John M. James , Consuelo Fernandez-Rodriguez and Julia Rodriguez 170.106.202.8 1Hospital Universitario Doce de Octubre, Madrid, Spain 2Colorado Allergy and Asthma Centers, Fort Collins, CO, USA , on 25 Sep 2021 at 16:08:59 Nuts are a well-defined cause of food allergy, which affect approximately 1 % of the general population in the UK and the USA. There do appear to be differences in the frequency of nut allergy between different countries because of different dietary habits and cooking procedures. For example, in the USA and France, peanuts are one of the most frequent causes of food allergy, but in other countries, it seems to be less common. Genetic factors, in particular, appear to play a role in the development of peanut allergy. While the majority of nut allergens are seed storage proteins, other nut allergens are profilins and pathogenesis-related protein homologues, considered as panallergens because of their widespread distribution in plants. The presence of specific IgE antibodies to several nuts is a common clinical finding, but the clinical relevance of this cross-reactivity , subject to the Cambridge Core terms of use, available at is usually limited. Allergic reactions to nuts appear to be particularly severe, sometimes even life-threatening, and fatal reactions following their ingestion have been documented. Food allergy is diagnosed by identifying an underlying immunological mechanism (i.e. allergic testing), and establishing a causal relationship between food ingestion and symptoms (i.e. oral challenges). In natural history investigations carried out in peanut-allergic children, approximately 20 % of the cases outgrew their allergy or developed oral tolerance. The treatment of nut allergies should include patient and family education about avoiding all presentations of the food and the potential for a severe reaction caused by accidental ingestion. Patients and families should be instructed how to recognise early symptoms of an allergic reaction and how to treat severe anaphylaxis promptly. Peanut allergy: Nut allergy: Tree nut allergy: Allergens: Food allergy Nut and tree nut consumption has been proven to be a healthy prevalence of peanut allergy. They could also be related to dietary habit. For example, several studies show that nuts have the frequency of reactions produced by inadvertent ingestion a beneficial effect on the outcome of coronary disease and in more than 50 % of patients allergic to peanuts and in 15– https://www.cambridge.org/core/terms cholesterol serum levels. However, nuts and tree nuts are 30 % of patients allergic to other nuts in the years following among the highest producers of IgE-mediated allergic reac- diagnosis and dietary avoidance of nuts. tions following food ingestion (Table 1). Food allergy is esti- mated to affect approximately 6–8 % of children below 4 years Epidemiology of age and 1—2 % of individuals over the first decade of life. In the United States, food allergy produces approximately Nuts are the foods that most frequently cause fatal anaphylac- 30 000 anaphylactic reactions and 200 fatalities per year tic reactions. A recent analysis of thirty-two fatal food allergic (Sampson, 2002). Especially in the United States, peanut reactions in the United States from 1994–1999 showed pea- allergy has emerged as an important health problem, with con- nuts and other nuts to be responsible for 63 and 31 % of the siderable consequences for patients, families, schools, health deaths, respectively. All fatalities in patients over 6 years of . https://doi.org/10.1017/BJN20061869 care professionals and the food industry. Moreover, it has age were caused by this food group (Bock et al. 2001). Sur- recently been demonstrated that peanut allergy has a signifi- veys carried out in the UK and the United States showed an cant impact on quality of life and family relationships, similar estimated prevalence of allergic reactions to nuts of approxi- to some rheumatologic diseases (Primeau et al. 2000). Aller- mately 1 % in the general population. A cohort of 1218 new- gic reactions to nuts other than peanuts seem to be less fre- borns followed up to 4 years of age in the Isle of Wight quent although their role as a cause of severe or fatal yielded a percentage of 0·7 % with clinically-important reac- reactions has been well documented. tions to nuts (six to peanuts, one to hazelnuts and one to cash- In the last few years there has been an increase in nut and ews) (Tariq et al. 1996). A random-digit telephone survey of tree nut consumption because of their favourable health 4374 households in the United States provided information effects. The production of processed foods containing nuts about 12 032 individuals, and the prevalence of food allergy as components has also increased. This could facilitate con- to nuts was estimated to be 1·1 % (Sicherer et al. 1999). tamination of other food products being handled in the same Both of these investigations were based on reactions reported food manufacturing line (Teuber et al. 2003). These by participants without any further diagnostic procedures; facts could be important causes of the apparent increase in therefore the actual prevalence could have been overestimated. * Corresponding author: Jesus F. Crespo, fax þ34 913908261, email [email protected] Downloaded from https://www.cambridge.org/core S96 J. F. Crespo et al. Table 1. Nuts and tree nuts implicated in IgE-mediated reactions habits in the development of specific food allergy. Differences in cooking methods commonly related to cultural factors may Family Species Common name also contribute to the increase in prevalence of nut allergy Leguminoseae Arachis hypogea Peanut observed in different countries. For example, peanut allergy . IP address: Betulaceae Corylus avellana Hazelnut is not common in China although its consumption per capita Anacardiaceae Anacardium occidentale Cashew is similar to that in the United States. Most of the peanuts con- Pistacia vera Pistachio sumed in the latter country are dry roasted, including those Juglandaceae Juglans regia Walnut used to process peanut butter, while in China peanuts are gen- 170.106.202.8 Carya illinoinensis Pecan nut* Rosaceae Prunus dulcis Almond* erally boiled or fried before consumption. The higher tempera- Lecythidaceae Bertholletia excelsa Brazil nut tures produced in the dry-roasting process (1508C) compared Fagaceae Castanea sativa Chestnut* to boiling (1008C) or frying (1208C) increase the allergenic Pinaceae Pinus pinea Pine nut* potency of three major allergens of peanuts (Beyer et al. , on Proteaceae Macadamia intergrifolia Macadamia nut* 25 Sep 2021 at 16:08:59 Palmaceae Cocos nucifera Coconut* 2001). Moreover, the difference in frequency of peanut allergy in China and the United States does not appear to be due to * Infrequent or anecdotally described as causing allergic reactions. genetic factors, as the prevalence in the Chinese population living in the United States is similar to that observed in the American population. In a more recent study carried out in the Isle of Wight in chil- In contrast, it has been established that genetic factors may dren of 3–4 years of age, clinical allergy to peanuts was estab- exert an influence on the development of peanut allergy. In , subject to the Cambridge Core terms of use, available at lished by oral challenges to be 1·5 % (Grundy et al. 2002). studies carried out in the UK, the frequency of this condition With this in mind, it has been suggested that the incidence has been found to be significantly higher in relatives of peanut of peanut allergy could have increased in the last few years. allergy patients than in the general population (7 % v. 0·5 %). In a study carried out in a population from the UK, a signifi- There is also a possible association with HLA class II genes cant increase in the prevalence of peanut allergy assessed by (Howell et al. 1998). In a study carried out in fifty-eight skin testing was found, ranging from 1·1 % in 1989 to 3·3 % pairs of twins, 7 % of dizygotes shared peanut allergy v. in 1994–1996. The reported prevalence of clinical allergy to 64 % monozygotes, which suggests a significant genetic influ- peanut increased from 0·5 to 1 % in this period of time, ence. The probability of inheriting peanut allergy was esti- although the differences were not significant (Grundy et al. mated to be 81·6 %, a percentage similar to other allergic 2002). The increase in peanut sensitisation may be related to diseases, such as asthma (87 %), atopic dermatitis (74 %) earlier exposure to the allergen, the availability of more and allergic rhinitis (74–82 %) (Sicherer et al. 2000). food products containing small amounts of peanuts and their presence in foods frequently consumed in childhood, such as peanut butter. Immunopathology In general, the prevalence of adverse reactions to foods is IgE-mediated reactions are the most extensively studied and https://www.cambridge.org/core/terms higher in children than in adults. Surveys carried out in the best defined group of all food adverse reactions. A failure in general population, however, show that allergy to nuts is an development, or a breakdown of oral tolerance, leads to an important problem in adulthood. In the UK, the perceived increased production of specific IgE antibodies, which bind prevalence of peanut allergy ranges between 0·61 % in chil- to high-affinity IgE receptors (FceI) on the surface of mast dren below 14 years of age, 0·53 % in individuals from 15 cells, basophils, Langerhans cells and monocytes of atopic to 44 years and 0·3 % in adults over 44 years, with a signifi- subjects.