Peanuts and tree nuts

Introduction

Over the last few decades, peanuts have become a ubiquitous part of the Western diet as they are a versatile form of easily digested protein (Lucas 1979). In a study looking at the use of dietary manipulation to prevent the development of food allergy, all infants in the control group were exposed to whole peanuts by their second birthday (Zeiger et al. 1989); occult exposure probably occurs even earlier. Adverse reactions to peanuts and tree nuts are generally IgE mediated, occurring rapidly with subjects presenting with dermatological, respiratory and gastrointestinal manifestations (Hourihane et al. 1997). Peanuts and tree nuts are responsible for a third of all admissions with anaphylaxis (Bock 1992). Peanuts are part of the legume family, they are more closely related to peas, beans, soy and lentils than the tree nuts. It has been suggested that there is extensive cross-reactivity between peanut and tree nuts in terms of sensitisation but not clinical reactivity (Sampson and McCaskill 1985, Bernhisel-Broadbent and Sampson 1989). However a recent British survey suggested that 50% of people with peanut allergy have symptoms with other nuts (Loza and Brostoff 1995). For the legume family, most subjects show sensitisation to at least two members of the family but very few subjects are clinically allergic to more than one (Bernhisel-Broadbent and Sampson 1989).

Prevalence and natural history

Peanut and tree nut allergy generally presents in childhood (Sampson 1990, Kivity et al. 1994). The majority of children react to peanut on their first

Table 10.1 Epidemiology of adverse food reactions to cows'

Author, date Type of study

Country

Halpern et al. 1973

Dean 1997

Arshad et a/1993

Burr and Merrett 1983

Young et al. 1994

Niestijl Jansen et al. 1994

Bjornsson et al. 1996

Prospective series USA

Population based, birth UK cohort

Population based, birth UK cohort

Population based, cross- UK sectional

Population based, cross- UK sectional

Population based, cross- Holland sectional

Population based, cross- Sweden sectional

Kajosaari 1982 Population based, cross- Finland sectional milk - key studies

No. of subjects Point prevalence Cumulative incidence

Definition

1084 1218 1174 475 18 880 1483 1812

1% in adults

2.7%, all age groups

1% (sp IgE) 0.07% (sp IgE and symptoms) aged 20-44y

History History History History History History

Sp IgE ± history

Open challenge at home

Kivity et al. 1994 Retrospective series

Gerrard et al. 1973

Prospective series

Schrander et al. Population based, birth cohort

1993

Jakobson and Lindberg 1979

Bock 1987

Population based, birth cohort

Population based, birth cohort

Israel, recent onset symptoms to food

Canada Netherlands Sweden USA

Host and Halken Population based, birth Denmark 1990 cohort

112

0%, 10-48y

Open or double-blinded challenges

787

7.5%

Open challenge at home

1158

2.3% to ly

Open challenge

1079

1.9% to ly

Open challenge

480

15% to 3y (history) 2.2% to 3y (challenge)

double-blinded challenge

1749

2.2% to 3y

Open or double-blinded challenges

Table 10.2 Combined cows' milk and soy allergy - key studies

Author, date

Country

Number of

Basis of diagnosis

Basis of diagnosis

Prevalence of soy

Comments

subjects

of cows' milk

of soy allergy

allergy in children

allergy

with proven

cows' milk

allergy

Kuitunen et al.

UK

35

Open challenge

Open challenge

11%

Non-IgE, mean age

1975

5m

Perkkio et al.

Italy

103

Open challenge

Open challenge

11%

Non-IgE

1981

Bardare et al.

France

29

Open challenge

Open challenge

17%

Mixed

1988

Paganus et al.

Finland

19

Open challenge

Open challenge

32%

Mixed, mean age

1992

11m

Zeiger et al. 1999

USA

93

Open or blinded

Open or blinded

14%

Mainly IgE, mean

food challenge

challenge

age 19m

Table 10.3 Epidemiology of adverse food reactions to soy - key studies

Author, date Type of study Country No. of Point prevalence Cumulative Definition subjects incidence

Dean 1997

Population based, birth cohort

UK, unselected

1218

0% at 1y; 0% at 2y; 0% at 4y

0% to 4y

History

Young et al. 1994

Population based, cross-sectional

UK

18880

0.3%, all age groups

History

Niestijl Jansen et al. 1994

Population based, cross-sectional

Holland

1483

0%, 18-70y

History

Bjornsson et al. 1996

Population based, cross-sectional

Sweden

1812

2% (sp IgE) 0% (sp IgE and symptoms) aged 20-44y

Sp IgE ± history

Giampietro et al. 1992

Prospective series

Italy, atopic children

317

3%, 1m to 10y

Open challenge

Kivity et al. 1994

Retrospective series

Israel, recent onset symptoms to foods

112

0%, 10-48y

Open or double-blinded challenges

Magnolfi et al. 1996

Prospective series

Italy, atopic children

704

21% by SPT, 1.1% by DBPCFC 1m to 18y

Double-blinded challenge

Sampson 1988

Prospective series of children with eczema

USA

204

5%

Double-blinded challenges

Bruno et al. 1997

Prospective series, multi-centre

Italy - infants with history suggestive of food allergy

505

1.2% at 6m to 14y

Double-blinded challenge

Bock 1987

Population based, birth cohort

USA (middle-class community)

480

2.2% to 3y (history) 0.4% to 3y (challenge)

double-blinded challenge

Table 10.4 Epidemiology of adverse food reactions to peanut and tree nuts - key studies

Author, date Type of study Country No of subjects Point prevalence Cumulative Definition incidence

Burr and Merrett 1983

Population based, cross-sectional

UK

475

0% adults

History

Foucard 1991

Cross-sectional medical students

Sweden

1050

9%

History

Young etal. 1994

Population based, cross-sectional

UK

18 880

1.7% (all nuts) in all ages

History

Niestijl Jansen et al. 1994

Population based, cross-sectional

Holland

1483

0% adults

History

Emmett et al. 1999

Population based, cross-sectional

UK

46 252

0.61% (0-4y) 0.53% (15-44y) 0.30% (>44y)

History

Tariq etal. 1996

Population based, birth cohort

UK

1456

1.3% (SPT) at 4y 1.1% (history and SPT) at 4y

See left

Kajosaari 1982

Population based, cross-sectional

Finland

802

2% at 1y 1% at 2y 2% at 3y 0% at 6y

Open challenge at home

Munoz-Furlong et Population based, cross- USA al. 1989 sectional

Bjornsson et al. Population based, cross- Sweden 1996 sectional

12 032 1812

Kivity et al. 1994 Retrospective series

Golding et al. Population based, birth 1998 cohort

Israel, recent onset symptoms with food

14 000

Bock 1987 Population based, birth cohort

History via telephone interview

Sp IgE ± history

Open or double-blinded challenges

Double-blinded food challenge

double-blinded challenge known exposure. Sensitisation must therefore be due to occult exposure (Hourihane et al. 1997). Reactions to peanuts and tree nuts are relatively common. Up to 2% of infants have histories of adverse reactions to peanuts with the highest prevalence figures being seen around four years of age (Table

10.4). Rates in adults appear to be lower unless a highly selected atypical population is studied (Foucard 1991). Where challenges are used to confirm the diagnosis, the prevalence figures drop to under 0.7% (Table 10.4). Historically, peanut and tree nut allergies have been considered to be lifelong problems (Sampson and Scanlon 1989, Bock and Atkin 1989). However, recently, evidence has been presented to suggest that at least some children outgrow their allergy by five years of age (Golding et al. 1998, Hourihane et al. 1998). This is supported by the evidence that the prevalence of peanut allergy is lower in adults (Table 10.4).

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