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Objectives: To determine whether there are any differences between children who remain mildly or moderately allergic to peanut and children with similar histories but a negative reaction on challenge with peanut., Design: Case-controls matched for age and sex., Setting: Children's day wards in two teaching hospitals., Intervention: Open food challenge with peanut., Subjects: 15 children with resolved peanut allergy (resolvers) and 15 with persistent allergy (persisters)., Main Outcome Measure: Reaction on challenge with peanut, serum total and peanut specific IgE concentrations., Results: The groups had a similar median age at first reaction to peanut (11 months, range 5-38) and similar symptoms. Allergy to other foods was less common in resolvers (2/15) than persisters (9/15) (P=0.02). On skin prick testing with peanut all 13 resolvers tested but only 3/14 persisters had a weal of <6 mm (P<0.0001). Total and peanut specific IgE concentrations did not differ much between the groups., Conclusion: Appropriately trained clinicians must be prepared to challenge preschool children with peanut as some will be tolerant despite a history of reactions to peanut and a positive skin prick test with peanut. Preschool children whose apparent peanut allergy is refuted by food challenge show allergy to other foods less often than those in whom peanut allergy persists. The size of weal on skin prick testing to peanut predicts reactivity but not severity on peanut challenge.

Objective: To determine the in vivo allergenicity of two grades of peanut oil for a large group of subjects with proved allergy to peanuts., Design: Double blind, crossover food challenge with crude peanut oil and refined peanut oil., Setting: Dedicated clinical investigation unit in a university hospital., Subjects: 60 subjects allergic to peanuts; allergy was confirmed by challenge tests., Outcome Measures: Allergic reaction to the tested peanut oils., Results: None of the 60 subjects reacted to the refined oil; six (10%) reacted to the crude oil. Supervised peanut challenge caused considerably less severe reactions than subjects had reported previously., Conclusions: Crude peanut oil caused allergic reactions in 10% of allergic subjects studied and should continue to be avoided. Refined peanut oil did not pose a risk to any of the subjects. It would be reasonable to recommend a change in labelling to distinguish refined from crude peanut oil.

Objectives: To determine rates of other atopic manifestations in people with peanut allergy and the prevalence of such allergy in their families., Design: A survey of people with self reported peanut allergy and people referred by their general practitioner for suspected peanut allergy; survey and skin testing of 50 children with reported peanut allergy and their available first degree relatives., Subjects: 622 adults and children with reported, suspected, or known peanut allergy., Main Outcome Measures: Prevalence of peanut allergy and other allergies in the families of people with peanut allergy., Results: 622 valid completed questionnaires were returned out of the 833 questionnaires dispatched (74.7%). All forms of atopy were both more common in successive generations (P < 0.0001) and more common in maternal than paternal relatives (P < 0.0001). Peanut allergy was reported by 0.1% (3/2409) of grandparents, 0.6% (7/1213) of aunts and uncles, 1.6% (19/1218) of parents, and 6.9% (42/610) of siblings. Consumption of peanuts while pregnant or breast feeding was more common among mothers of probands aged < or = 5 years than mothers of probands aged > 5 years (P < 0.001). Age of onset correlated inversely with year of birth (r = -0.6, P < 0.001). Skin prick testing of 50 children with reported peanut allergy and their families: 7 probands (14%) had a negative result for peanut. Peanut allergy was refuted by food challenge in all those tested (5/7). No parent and 13% (5/39) of siblings had a positive result on skin prick testing for peanut. Two of these siblings had negative challenge with peanuts. The prevalence of peanut allergy in siblings is therefore 3/39 (7%)., Conclusions: Peanut allergy is more common in siblings of people with peanut allergy than in the parents or the general population. Its apparently increasing prevalence may reflect a general increase of atopy, which is inherited more commonly from the mother. Peanut allergy is presenting earlier in life, possibly reflecting increased consumption of peanut by pregnant and nursing mothers.

Objective: To determine the prevalence of sensitisation to peanuts and tree nuts in all children born during one year in one geographical area., Design: Birth cohort study with structured review at ages 1, 2, and 4 years., Setting: All children born on the Isle of Wight between January 1989 and February 1990., Subjects: Of 1456 children originally included, 1218 were reviewed at age 4 years. Of these, 1981 had skin prick tests., Main Outcome Measures: Positive skin test results, clinical atopic disease, and risk factors for the development of atopy., Results: 15 of 1218 (1.2%) children were sensitised to peanuts or tree nuts (13 to peanuts). Six had had allergic reactions to peanuts (0.5% of the population), one to hazelnuts, and one to cashew nuts; three had had anaphylactic reactions. Seven children had positive skin test results or detectable IgE to peanuts without clinical symptoms. Two children who reacted to peanut in infancy had lost their sensitivity by 4 years. Family history of atopy, allergy to egg (odds ratio 9.9, 95% confidence interval 2.1 to 47.9, and eczema (7.3, 2.1 to 26.1) were important predictors for peanut allergy., Conclusions: IgE mediated allergy to peanuts is common in early childhood. In many the allergy persists but a minority may develop tolerance.

Objective: To investigate clinical features of acute allergic reactions to peanuts and other nuts., Design: Analysis of data from consecutive patients seen by one doctor over one year in an allergy clinic at a regional referral centre., Subjects: 62 patients aged 11 months to 53 years seen between October 1993 and September 1994., Main Outcome Measures: Type and severity of allergic reactions, age at onset of symptoms, type of nut causing allergy, results of skin prick tests, and incidence of other allergic diseases and associated allergies., Results: Peanuts were the commonest cause of allergy (47) followed by Brazil nut (18), almond (14), and hazelnut (13). Onset of allergic symptoms occurred by the age of 2 years in 33/60 and by the age of 7 in 55/60. Peanuts accounted for all allergies in children sensitised in the first year of life and for 82% (27/33) of allergies in children sensitised by the third year of life. Multiple allergies appeared progressively with age. The commonest symptom was facial angioedema, and the major feature accounting for life threatening reactions was laryngeal oedema. Hypotension was uncommon. Of 55 patients, 53 were atopic--that is, had positive skin results of tests to common inhaled allergens--and all 53 had other allergic disorders (asthma, rhinitis, eczema) due to several inhaled allergens and other foods., Conclusions: Sensitisation, mainly to peanuts, is occurring in very young children, and multiple peanut/nut allergies appear progressively. Peanut and nut allergy is becoming common and can cause life threatening reactions. The main danger is laryngeal oedema. Young atopic children should avoid peanuts and nuts to prevent the development of this allergy.