Are cashew allergies typically triggered by proteins also found in other tree nuts?

1. How cashew allergy works — the protein culprits

Allergic reactions to cashews occur when immune IgE antibodies recognise specific cashew proteins; three major cashew allergens have been characterised as Ana o 1 and Ana o 2 (cupin family) and Ana o 3 (prolamin/2S albumin family), and these are considered the principal triggers of clinical reactions including anaphylaxis ^{[1] [3] [7]}.

2. Cross‑reactivity: cashew and its close botanical relatives

Laboratory and clinical work show clear IgE cross‑reactivity between cashew and pistachio, reflecting their close botanical relationship (both Anacardiaceae) and shared allergenic proteins; many clinical sources emphasise that people allergic to cashew frequently react to pistachio and vice versa ^{[4] [5] [8] [6]}.

3. Beyond pistachio: other Anacardiaceae and unexpected partners

Studies looking at cashew‑sensitised sera report cross‑sensitisation to related Anacardiaceae such as pink peppercorn and mango, with in‑vitro evidence that certain albumin‑ and legumin‑type seed storage proteins can bind cashew‑specific IgE ^[5]. Clinical relevance (i.e., whether in‑vitro binding produces symptoms on ingestion) varies by patient and is not uniformly established in the sources ^[5].

4. Cross‑reactivity across the wider tree‑nut group is mixed

Reviews and population studies show that while many tree‑nut allergic individuals are sensitised to multiple nuts, cross‑reactivity patterns depend on protein family homology: storage proteins (11S/7S/2S) and certain defense proteins drive cross‑reactivity among some nuts, but cashew/pistachio pairings are stronger than cashew with, for example, walnut or almond, which are more distantly related ^{[5] [6] [9]}.

5. What testing can and cannot tell you

Component‑resolved diagnostics measuring IgE to specific proteins (e.g., Ana o 3 for cashew) improve specificity for cashew allergy and help predict likely clinical allergy, but they do not perfectly predict reaction severity or guarantee cross‑reactivity outcomes for every other nut ^{[2] [8]}. In vitro cross‑binding (sensitisation) does not always equal clinical reactivity — food challenges remain the reference for proving true cross‑allergy in many studies ^{[5] [10]}.

6. Clinical and public‑health implications — avoidance and labeling

Because cashew allergy can provoke severe reactions and because co‑allergy with pistachio is common, many clinicians counsel avoidance of both when cashew allergy is confirmed; broader avoidance of all tree nuts is often recommended unless testing/food challenge shows tolerance ^{[4] [11] [12]}. Regulatory labeling and guidance on tree nuts have been evolving (FDA guidance noted in patient resources) and affect how consumers identify risks on packaged foods ^{[4] [12]}.

7. Where the reporting is limited or contested

Available sources describe strong cashew–pistachio cross‑reactivity and some cross‑sensitisation to other Anacardiaceae ^[5], but they also show heterogeneity in rates of multi‑nut clinical allergy (reports range across cohorts and methods) and note that in‑vitro findings don’t always translate to clinical symptoms ^{[5] [6]}. Systematic reviews point to increasing cashew allergy prevalence but call the overall evidence levels variable ^[3].

8. Practical takeaways for patients and clinicians

If someone is allergic to cashew, clinicians commonly test for pistachio and consider component testing (Ana o 3) to refine diagnosis; many allergy specialists advise caution around other tree nuts until tolerance is demonstrated, because protein homologies can cause cross‑reactivity in a substantial minority of patients ^{[2] [8] [9]}. For definitive determination of which additional nuts will provoke symptoms, supervised oral food challenges remain necessary where clinical uncertainty exists (not found in current reporting as a specific procedural guideline here).

Limitations: this summary uses the provided literature and patient‑facing resources; available sources do not mention randomised head‑to‑head trials proving clinical cross‑reactivity for every nut pair, and reported rates vary by study design and population ^{[5] [3]}.