Cross-reactivity in allergic reactions occurs when the proteins in one substance are similar to the proteins found in another. Because peanuts and soy are both legumes, there is concern that peanut-sensitive individuals will also react to soy. However, clinical studies indicate that cross-reactivity between peanut and soy is a relatively infrequent occurrence. According to the University of Manchester, “Most soy allergic individuals are tolerant of peanut …This does not mean that absolutely no patients exist that demonstrate cross-reactive allergy to multiple legumes, but it is rare.”
Allergen cross-reactivities occur when IgE antibodies, originally raised against a specific allergen, bind to identical or highly similar surface areas of another related allergen. These cross-reactivities are largely determined by secondary and tertiary structural similarities between allergens. The general thinking is that cross-reactivity requires more than 70% sequence identity, while proteins that share less than 50% sequence identity are rarely cross-reactive. This also implies that cross-reactive proteins have a similar three-dimensional fold and belong to the same protein family.1 As somewhat of a side note, there is also evidence indicating that IgE cross-reactivity exists between unrelated allergens, although that type of cross-reactivity is less common.2
Research into the cross-reactivity between peanuts and soy has been underway for many decades. For example, in 1985, Sampson and McCaskill3 found that among 113 children with atopic dermatitis evaluated with double-blind, placebo-controlled, oral food challenges (DBPCFCs), only 1 (0.8%) had clinical allergy to both peanuts and soy, despite 19% reacting to peanut and 5% to soy. In 1989, Bock and Atkins4 studied 32 children with peanut allergy confirmed by DBPCFCs and found that 10 (31%) had a positive skin prick test (SPT) to soy, but only 1 (3%) of those with peanut allergy had a clinical reaction to soy. This study illustrates two important points. One, clinical reaction to soy in peanut-sensitive individuals is relatively uncommon and two, the rate of positive SPTs to soy is much greater than rate of clinical reaction. This is true in peanut-sensitive individuals as well as non-peanut-sensitive individuals. 5,6
Several other studies in addition to the ones by Sampson and McCaskill3 and Bock and Atkins4 have found that clinical reaction to soy in peanut-sensitive individuals is relatively rare and that positive SPTs to soy are much more common than clinical reactions.7,8 Also, although all four of the studies cited above were conducted in the U.S., the results of European studies are similar. For example, in France, Moneret-Vautrin et al.9 found that of 142 (50 diagnosed by DBPCFC) peanut-sensitive individuals, most of whom were below 15 years of age, 14 had a positive SPT to soy whereas only 2 (1.4%) responded clinically.
Finally, and most recently, in the United Kingdom, Patel et al.10 examined the cross-reactivity between peanut and soy in 64 individuals aged 8-16 years, all of whom reacted to peanut in response to a DBPCFC, 15 (22%) of which with anaphylaxis. Of the 64 patients, 2 (~3%) experienced objective symptoms to roasted soy (experiencing mild objective symptoms at cumulative 1 g soy protein).
In conclusion, among the eight major allergenic foods (milk, eggs, fish, crustacean shellfish, tree nuts, peanuts, wheat and soybean) in the U.S., the prevalence of soy among adults11 and children12,13 is the lowest. As reviewed, research published over the past 3 decades shows that among individuals allergic to peanuts, relatively few– certainly less than 5%– will also be allergic to soy.
- Aalberse RC, Akkerdaas J, van Ree R. Cross-reactivity of IgE antibodies to allergens. Allergy. 2001;56(6):478-90.
- Bublin M, Breiteneder H. Cross-reactivities of non-homologous allergens. Allergy. 2019.
- Sampson HA, McCaskill CC. Food hypersensitivity and atopic dermatitis: evaluation of 113 patients. J Pediatr. 1985;107(5):669-75.
- Bock SA, Atkins FM. The natural history of peanut allergy. J Allergy Clin Immunol. 1989;83(5):900-4.
- Magnolfi CF, Zani G, Lacava L, et al. Soy allergy in atopic children. Ann Allergy Asthma Immunol. 1996;77(3):197-201.
- Celakovska J, Krcmova I, Bukac J, et al. Sensitivity and specificity of specific IgE, skin prick test and atopy patch test in examination of food allergy. Food Agricultural Immunol. 2017;28(2):238-47.
- Bernhisel-Broadbent J, Sampson HA. Cross-allergenicity in the legume botanical family in children with food hypersensitivity. J Allergy Clin Immunol. 1989;83(2 Pt 1):435-40.
- Burks AW, James JM, Hiegel A, et al. Atopic dermatitis and food hypersensitivity reactions. J Pediatr. 1998;132(1):132-6.
- Moneret-Vautrin DA, Rance F, Kanny G, et al. Food allergy to peanuts in France–evaluation of 142 observations. Clin Exp Allergy. 1998;28(9):1113-9.
- Patel N, Vazquez-Ortiz M, Lindsley S, et al. Low frequency of soya allergy in peanut-allergic children: relevance to allergen labelling on medicines. Allergy. 2018.
- Gupta RS, Warren CM, Smith BM, et al. Prevalence and severity of food allergies among US adults. JAMA Netw Open. 2019;2(1):e185630.
- Gupta RS, Warren CM, Smith BM, et al. The public health impact of parent-reported childhood food allergies in the United States. Pediatrics. 2018;142(6).
- McGowan EC, Keet CA. Prevalence of self-reported food allergy in the National Health and Nutrition Examination Survey (NHANES) 2007-2010. J Allergy Clin Immunol. 2013;132(5):1216-9 e5.