Pecan nut
Summary
Pecan is a deciduous monoecious nut tree belonging to the genus Carya of the family Juglandaceae. Carya illinoinensis (pecan nut) is the most widely cultivated economical edible nut crop. The pecan tree is native to North America, however, it is also cultivated in other countries, such as Australia, Brazil, China, Israel, Peru, Argentina and South Africa. The prevalence of pecan nut allergy is increasing with its existence in the United States, Canada, Australia, Europe, Israel, etc. Oral ingestion of pecan nuts can lead to IgE-mediated allergic reactions like oral food allergy and even severe reactions like anaphylaxis. Three allergenic components, i.e., Car i 1 (2S albumin), Car i 2 (vicilin-like protein) and Car i 4 (legumin-like protein) have been identified for pecan nut allergy. There is a high prevalence of co-allergy between walnuts and pecan nuts and is found to be strongly correlated since the allergens from both have high sequence identity. Patients with walnut allergy are at a very high risk of having pecan nut allergy too. Further, cross-reactivity with other tree nuts (e.g., hazelnut and macadamia) and tree pollens (e.g., birch) have also been reported.
Epidemiology
Worldwide distribution
In United States (US), the prevalence of total tree nut allergy in the general population by a telephone survey was found to be 0.6%, with pecan nut allergy reported in 31% of tree-nut allergic individuals. Another telephone survey was conducted in 10 Canadian provinces and the results showed that the self-reported prevalence of tree nut allergy was found to be 1.73% in children and 1.07% in adults.
In a cross-sectional study conducted in Australia, the prevalence of food allergies in 116 school-going children (10-14 years) was assessed. The results reported that the prevalence of pecan nut allergy in these children was found to be 0.2%.
The Pronuts study was a multicenter, European study (London, Geneva and Valencia) that reported the pecan nut allergy in 31.9% nut allergic individuals, with the maximum pecan nut allergy found in Valencia (66.7%). The overall consumption of pecan among all centers was only 6% and was not considered as index nut. Furthermore, in a cross-sectional study conducted in Mexico (n=1126), the probable pecan allergy was reported to be 0.3%.
A prospective cohort study conducted on 83 tree nut allergic patients in Israel found 57 patients sensitized to pecan, with the clinical allergy to pecan nut reported to be 59.6%. Further, a study was conducted to assess the cross-sensitization profiles of tree nuts in birch endemic areas in Finland. The results reported that the prevalence of pecan nut allergy in tree nut allergic subjects with and without birch sensitization was found to be 21% and 8%respectively.
Risk factors
Pecan and walnut allergy are found to be strongly correlated since the allergens from both have high sequence identity. A high prevalence of co-allergy between walnuts and pecan nuts have been reported. In a study evaluating 60 multi-allergic pediatric patients, only 3 out of 32 walnut allergic patients could tolerate pecan. The Jaccard similarity coefficient for the co-occurrence of walnut and pecan nut allergy was found to be 0.91. Further, the NUT-CRACKER (NUT Co Reactivity—ACquiring Knowledge for Elimination Recommendations) study, which was a prospective cohort study (n=83) reported that two-third of walnut allergic individuals were allergic to pecan also. Moreover, walnut-pecan allergic patients usually suffer from more gastrointestinal reactions on oral challenge test with walnut.
Route Of Exposure
Main
Oral ingestion of pecan nuts can lead to immunoglobulin (IgE)-mediated allergic reactions like oral food allergy and even severe reactions like anaphylaxis.
Clinical Relevance
Oral allergy symptoms and Anaphylaxis
In a study conducted on 25 double-blind placebo-controlled food challenge (DBPCFC) positive pecan allergic patients, oral allergy symptoms were depicted as urticaria (36%) and gastrointestinal reactions (24%). In another study conducted on 60 multi-allergic pediatric patients, DBPCFC was performed on 30 patients for pecan, of which 29 showed oral food allergy symptoms. The oral food challenge reported skin reactions, gastrointestinal reactions and respiratory reactions in 93%, 41% and 3% respectively. Anaphylaxis due to walnut-pecan allergy was reported in 53.1% of 49 patients subjected to oral food challenge in a prospective study conducted in Israel. In the same study of 49 walnut-pecan allergic patients, the oral food challenge depicted skin reactions in 67.3%, gastrointestinal problems in 46.9% and upper and lower respiratory tract infection in 49% and 20.4%.
Allergic rhinitis
Allergic rhinitis was reported in 32% of pecan allergic patients confirmed by DBPCFC in a study.
Asthma
In a cross-sectional study conducted in 1126 individuals in Mexico, the history of asthma was found to be significantly associated with probable allergy to pecan nuts (p=0.009).
Asthma was reported in 24% of pecan allergic patients confirmed by DBPCFC in a study.
In a prospective cohort study conducted in Israel, asthma was reported in 44.9% of walnut-pecan allergic patients.
Atopic Dermatitis
A prospective cohort study reported atopic dermatitis in 59.2% of walnut-pecan allergic patients in Israel (Elizur, Appel.
Other diseases
Only two cases have reported the development of contact dermatitis as type I hypersensitivity reactions due to prolonged contact with pecans.
Cross-Reactivity
In the Pronuts study, walnut and pecan were found as highly correlated nut allergies, where 97% of pecan allergic individuals were found to be allergic to walnuts, while only 75% of walnut allergic children were allergic to pecans. The NUT-CRACKER and NUT-CRACKER-PS study was conducted in Israel to study coincidences of allergies among tree nuts and predict walnut-pecan allergy severity respectively. A total of 134 of 183 patients (47 from NUT-CRACKER and 87 from NUT-CRACKER-PS study) were found to be walnut allergic. Pecan allergy was co-existing in 79.9% of walnut allergic patients (3.6-27.3 years), while 100% of pecan allergic patients were allergic to walnut. This suggests the co-allergy to be unidirectional. The high association between walnut and pecan allergies (spearman coefficient=0.96) could be attributed to high sequence identity among the pecan allergens (Car i 1, Car i 2 and Car i 4) with their counterparts in walnut (Jug r 1, Jug r 2, Jug r 4) respectively. Pecan allergy was also found to be significantly correlated with hazelnut (Odd’s ratio [OR]=14.9, p<0.0001, Pearson correlation coefficient = 0.47) and macadamia nut (OR=15.2, p<0.0001, Pearson correlation coefficient=0.36), while it was found to be inversely related with peanut allergy (Pearson correlation coefficient = -0.25). Further, 66.7% of peanut-allergic patients showed negative results to specific skin prick tests for pecan. In a single-center, retrospective analysis of serum specific IgE levels to coconut, 51% of co-sensitization was reported between pecan and coconut but were not found to be significantly associated. A study conducted in Finland to determine cross-reactivities between birch pollen and tree nuts reported that 21% of subjects sensitized to birch pollens were sensitized to pecan also.
References
- Fabrizio G, Van der Watt E, Coetzer G. Propagation of Pecan (Carya illinoensis): A review. African Journal of Biotechnology. 2018;17:586-605.
- Sparks D. Adaptability of Pecan as a Species. HortScience: a publication of the American Society for Horticultural Science. 2005;40(5):1175-89.
- Fronza D, Hamann JJ, Both V, Anese RdO, Meyer EA. Pecan cultivation: general aspects. Ciência Rural. 2018;48(2):e20170179.
- Huang Y, Xiao L, Zhang Z, Zhang R, Wang Z, Huang C, et al. The genomes of pecan and Chinese hickory provide insights into Carya evolution and nut nutrition. GigaScience. 2019;8(5):1-17.
- Carya illinoinensis (pecan) [Internet]. CAB International. 2019 [cited November 9, 2020].
- Sharma GM, Irsigler A, Dhanarajan P, Ayuso R, Bardina L, Sampson HA, et al. Cloning and characterization of an 11S legumin, Car i 4, a major allergen in pecan. Journal of agricultural and food chemistry. 2011;59(17):9542-52.
- Sicherer SH, Muñoz-Furlong A, Godbold JH, Sampson HA. US prevalence of self-reported peanut, tree nut, and sesame allergy: 11-year follow-up. The Journal of allergy and clinical immunology. 2010;125(6):1322-6.
- Soller L, Ben-Shoshan M, Harrington DW, Fragapane J, Joseph L, St Pierre Y, et al. Overall prevalence of self-reported food allergy in Canada. The Journal of allergy and clinical immunology. 2012;130(4):986-8.
- Sasaki M, Koplin JJ, Dharmage SC, Field MJ, Sawyer SM, McWilliam V, et al. Prevalence of clinic-defined food allergy in early adolescence: The SchoolNuts study. The Journal of allergy and clinical immunology. 2018;141(1):391-8.e4.
- Brough HA, Caubet JC, Mazon A, Haddad D, Bergmann MM, Wassenberg J, et al. Defining challenge-proven coexistent nut and sesame seed allergy: A prospective multicenter European study. The Journal of allergy and clinical immunology. 2020;145(4):1231-9.
- Bedolla-Barajas M, Bedolla-Pulido TR, Macriz-Romero N, Morales-Romero J, Robles-Figueroa M. Prevalence of Peanut, Tree Nut, Sesame, and Seafood Allergy in Mexican Adults. Revista de investigacion clinica; organo del Hospital de Enfermedades de la Nutricion. 2015;67(6):379-86.
- Elizur A, Appel MY, Nachshon L, Levy MB, Epstein-Rigbi N, Golobov K, et al. NUT Co Reactivity - ACquiring Knowledge for Elimination Recommendations (NUT CRACKER) study. Allergy. 2018;73(3):593-601.
- Uotila R, Kukkonen AK, Pelkonen AS, Mäkelä MJ. Cross-sensitization profiles of edible nuts in a birch-endemic area. Allergy. 2016;71(4):514-21.
- Andorf S, Borres MP, Block W, Tupa D, Bollyky JB, Sampath V, et al. Association of Clinical Reactivity with Sensitization to Allergen Components in Multifood-Allergic Children. The journal of allergy and clinical immunology In practice. 2017;5(5):1325-34.e4.
- López-Calleja IM, de la Cruz S, González I, García T, Martín R. Market analysis of food products for detection of allergenic walnut (Juglans regia) and pecan (Carya illinoinensis) by real-time PCR. Food chemistry. 2015;177:111-9.
- Elizur A, Appel MY, Nachshon L, Levy MB, Epstein-Rigbi N, Pontoppidan B, et al. Clinical and Molecular Characterization of Walnut and Pecan Allergy (NUT CRACKER Study). The journal of allergy and clinical immunology In practice. 2020;8(1):157-65 e2.
- Zhang Y, Lee B, Du WX, Lyu SC, Nadeau KC, Grauke LJ, et al. Identification and Characterization of a New Pecan [Carya illinoinensis (Wangenh.) K. Koch] Allergen, Car i 2. Journal of agricultural and food chemistry. 2016;64(20):4146-51.
- Joyce KM, Boyd J, Viernes JL. Contact dermatitis following sustained exposure to pecans (Carya illinoensis): a case report. Cutis. 2006;77(4):209-12.
- Geiselhart S, Hoffmann-Sommergruber K, Bublin M. Tree nut allergens. Molecular immunology. 2018;100:71-81.
- Allergen Nomenclature "Carya illinoinensis (Pecan) - All Allergen" [Internet]. WHO/IUIS Allergen Nomenclature Sub-Committee. 2019 [cited November 9, 2020].
- Spiric J, Koppelman SJ, Knulst A, Nordlee JA, Taylor SL, Baumert JL. In vitro digestion and characterisation of 2S albumin and digestion-resistant peptides in pecan. International Journal of Food Science & Technology. 2018;53(6):1566-78.
- Smeekens JM, Bagley K, Kulis M. Tree nut allergies: Allergen homology, cross-reactivity, and implications for therapy. Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology. 2018;48(7):762-72.
- Mattison CP, Rai R, Settlage RE, Hinchliffe DJ, Madison C, Bland JM, et al. RNA-Seq Analysis of Developing Pecan (Carya illinoinensis) Embryos Reveals Parallel Expression Patterns among Allergen and Lipid Metabolism Genes. Journal of agricultural and food chemistry. 2017;65(7):1443-55.
- Masthoff LJ, Hoff R, Verhoeckx KC, van Os-Medendorp H, Michelsen-Huisman A, Baumert JL, et al. A systematic review of the effect of thermal processing on the allergenicity of tree nuts. Allergy. 2013;68(8):983-93.
- Goldberg MR, Appel MY, Nega R, Levy MB, Epstein-Rigbi N, Nachshon L, et al. A Prospective Validation of the NUT CRACKER Diagnostic Algorithm for Walnut and Pecan Allergy with Prediction of Severity. The journal of allergy and clinical immunology In practice. 2020:Oct 8:S2213-198(20)31090-4. Epub ahead of print.
- Randhawa I, Morphew T, Marsteller NL. Correlation of negative skin-prick test results for tree nuts and successful tree nut challenges among children with peanut allergy. Allergy and asthma proceedings. 2018;39(6):456-60.
- Polk BI, Dinakarpandian D, Nanda M, Barnes C, Dinakar C. Association of tree nut and coconut sensitizations. Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology. 2016;117(4):412-6.