There are no predictive values to provide validated statistics for likelihood of passing a food challenge and there is no commercial component testing for Brazil nut sensitivity to my knowledge. Ber e 1 testing has been described (Pastorello EA, Farioli L, Pravettoni V, et al. Sensitization to the major allergen of Brazil nut is correlated with the clinical expression of allergy. J Allergy Clin Immunol 1998;102:1021–7.). There is evidence that Brazil nut is a common food allergen, although the reference in the Ask the Expert Question from the archives (see below) does not reflect my clinical experience as find hazelnut and almond as more common problems.
Data on the predictive value of testing to Brazil nut is published (Ridout, see below). In this small cohort, 10 subjects had a negative skin test to Brazil nut and a specific-IgE of < 3.5 kU/L, similar to your patient. Three of the 10 had a positive response to an oral challenge, suggesting that your patient has a approximately 30% chance of experiencing a reaction to a Brazil nut challenge. I am not aware of any more recent data that would modify this risk, and these are very small numbers.
In summary, I would advise your patient and patient’s family that despite the negative skin test there is a risk of approximately 30% in challenging with Brazil nut. If the original reaction was severe, I would not recommend challenging with this level of risk. If the original reaction was mild, I might consider, but personally I would advise against the challenge since Brazil nuts can be avoided more easily than other nuts.
Ridout, S., et al. "The diagnosis of Brazil nut allergy using history, skin prick tests, serum-specific immunoglobulin E and food challenges." Clinical & Experimental Allergy 36.2 (2006): 226-232
Background: Allergy to Brazil nut is a relatively common nut allergy and can be fatal. However, the evidence is lacking regarding the best approach to its diagnosis.
Objective: We sought to determine the relative merits of history, skin prick testing, measurement of serum-specific IgE and challenge in the diagnosis of Brazil nut allergy.
Methods: Fifty-six children and adults with a history of an allergic reaction to Brazil nut or evidence of sensitization were investigated by questionnaire (n=56), skin prick tests (SPTs) (n=53), measurement of serum-specific IgE to Brazil nut (n=54) and double-blind, placebo-controlled labial, and if necessary oral, challenges (n=19).
Results: Brazil nut allergy occurred in highly atopic individuals of any age with a strong family history of atopy. In 24 of 56 (43%), the history of an immediate reaction was sufficient to make a diagnosis with confidence and an oral challenge was considered unsafe. Of the 19 subjects undertaking the ‘gold standard’ test of a double-blind, placebo-controlled, food challenge, all six subjects with a SPT of at least 6 mm had a positive challenge and all three subjects with a SPT of 0 mm had a negative challenge. In the remaining 10 (53%) subjects, where SPT was between 1 and 5 mm and serum-specific IgE was less than 3.5 kU/L, an oral challenge was performed resulting in three positive and seven negative challenges.
Conclusion: A combination of history, SPT and serum-specific IgE was adequate in achieving a diagnosis in the majority (77%) patients with suspected Brazil nut allergy. However, a doubtful history with SPT between 1 and 5 mm, or a serum-specific IgE less than 3.5 kU/L may require an oral challenge to help determine the risk of a Brazil nut allergic reaction.
Most common tree nuts to cause allergic reactions
Q: What are the most common tree nut allergies?
A: Unfortunately, there are no definitive data on the most common tree nuts to cause reactions. Almost all the information we have has been gleaned from surveys, and the results from these surveys can differ. Results are dependent upon the country assayed and other factors. In addition, none of these studies have involved extremely large numbers of patients. However, at least to give you some help in this regard, I will share with you the information from two such studies.
There is an abstract copied below from a survey taken in Britain and published in the British Medical Journal, and as you can see the nuts responsible for reactions in order of frequency were Brazil nut, almond, and hazelnut. On the other hand, data from a more recent United States survey(1) showed for tree nuts, the most common offenders, in descending order of frequency, were: Cashew, hazel, almond, walnut, macadamia, pistachio, pecan, pine, and Brazil nuts.
Thank you again for your inquiry and we hope this response is helpful to you.
BMJ 1996; 312 doi: 10.1136/bmj.312.7038.1074 (Published 27 April 1996) Cite this as: BMJ 1996;312:1074
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.
For tree nuts, they were cashew, hazel, almond, walnuts, macadamia, pistachio, pecan, pine, and Brazil nuts, also in decreasing order of frequency.
1. J Allergy Clin Immunol 2010; 126(2):324-331.
Phil Lieberman, M.D.
I hope this information is of help to you and your patient.
All my best.
Dennis K. Ledford, MD, FAAAAI