Botanical Characteristics of Cashew (Anacardium occidentale)
- Scientific Name: Anacardium occidentale
- Family: Anacardiaceae (Same family as poison ivy, mango, and pistachio)
- Common Names: Cashew nut, Marañón
- Native Region: Brazil (now widely cultivated in India, Vietnam, and Africa)
Tree and Fruit Description
- The cashew tree is an evergreen tropical tree that grows 10–12 meters (33–40 feet) tall.
- The cashew nut is actually the seed of the cashew apple, growing at the bottom of the fleshy fruit.
- The seed is encased in a hard shell containing cardol and anacardic acid, which can cause skin irritation (similar to poison ivy).
Cashew as a Food Allergen
Cashews are classified as a major food allergen by the U.S. FDA, requiring mandatory labeling.
Allergenic Proteins in Cashews
| Allergen | Protein family | Molecular weight (kDa) | Clinical relevance |
|---|---|---|---|
| Ana o 1 | Vicilin-like (7S globulin) | 50 | Storage-protein allergen |
| Ana o 2 | Legumin-like (11S globulin) | 55 | Storage-protein allergen |
| Ana o 3 | 2S albumin | 14 | Best single marker of clinical and severe cashew allergy; closely related to pistachio Pis v 1 |
| Ana o 4 | PR-10 (Bet v 1-related) | 17 | Birch-pollen related; usually mild |
| Ana o 5 | Non-specific lipid transfer protein (nsLTP1) | 9 | Stable; relevant in LTP sensitization |
Molecular and Clinical Properties of Cashew Allergens
- Ana o 3 (2S albumin) is the best single marker of clinical and severe cashew allergy. It is closely related to pistachio Pis v 1, which is the main reason cashew and pistachio allergy so often occur together.
- Ana o 1 (vicilin) and Ana o 2 (legumin) are storage proteins that also have pistachio counterparts (Pis v 3, and Pis v 2 / Pis v 5).
- Ana o 4 is a PR-10 (Bet v 1-related) protein and Ana o 5 a lipid transfer protein; they are less important for most cashew-allergic people.
| Allergen | Heat stability | Digestive stability | Effect of processing |
|---|---|---|---|
| Ana o 1 | Moderate to high | Moderate | Largely survives roasting |
| Ana o 2 | Moderate to high | Moderate | Largely survives roasting |
| Ana o 3 | High | High | Survives roasting and digestion |
| Ana o 4 | Low | Low | Usually destroyed by roasting or cooking |
| Ana o 5 | High | High | Survives cooking and digestion |
Symptoms of Cashew Allergy
Symptoms appear within minutes to an hour after ingestion.
Mild to Moderate Reactions
Important: wheezing, coughing or any trouble breathing — or symptoms in two or more body systems — is anaphylaxis, not a moderate reaction. Give epinephrine and call 911.
- Itchy mouth or swelling (with cashew this is not pollen-related oral allergy syndrome; it can be the first sign of anaphylaxis)
- Hives (Urticaria)
- Nausea, Vomiting, Diarrhea
- Facial Swelling (Angioedema)
Severe Reactions (Anaphylaxis) Epinephrine (auto-injector or nasal spray) is the first-line treatment for anaphylaxis.
- Drop in Blood Pressure (Hypotension)
- Severe Bronchoconstriction (Wheezing, Asthma)
- Throat Swelling (Laryngeal Edema)
- Cardiovascular Collapse (Anaphylactic Shock)
Cross-Reactivity of Cashews
Cashew allergens are very closely related to pistachio allergens, which is why cross-reactivity between the two nuts is so high. The minor allergens Ana o 4 (PR-10) and Ana o 5 (LTP) relate to birch-pollen and LTP proteins. Peanut and other tree-nut allergies often occur alongside cashew allergy, but usually as separate sensitizations rather than through shared epitopes.
| Source | Related proteins | What it means |
|---|---|---|
| Pistachio | Ana o 3 ↔ Pis v 1 (2S); Ana o 2 ↔ Pis v 2 / Pis v 5 (11S); Ana o 1 ↔ Pis v 3 (7S) | Very high — most cashew-allergic people react to pistachio. Avoid unless an allergist confirms tolerance. |
| Mango | Same plant family (Anacardiaceae) | Occasionally reported |
| Peanut, walnut, other tree nuts | Different storage proteins | Co-allergy is common but usually separate sensitization — assessed individually |
| Birch pollen | Ana o 4 (PR-10) ↔ Bet v 1 | Usually mild oral symptoms |
| Peach, apple (LTP foods) | Ana o 5 (LTP) | Possible in people sensitized to LTPs |
Diagnosis of Cashew Allergy
Skin Prick Test (SPT)
- Detects IgE-mediated hypersensitivity to cashew extract.
Serum IgE Testing
- Measures specific IgE to cashew and its components; Ana o 3 is the best marker of clinical allergy. Higher IgE levels make allergy more likely but do not predict how severe a reaction will be.
Oral Food Challenge (OFC)
- Gold standard for diagnosing food allergy.
- Performed under medical supervision.
Anaphylaxis: act fast. After an exposure, any breathing symptom (wheeze, repeated cough, throat tightness, hoarse voice), fainting or dizziness, or symptoms in two or more body systems (for example hives plus vomiting) is anaphylaxis — even without hives.
- Give epinephrine right away (auto-injector or nasal spray). Do not wait to see if symptoms get better.
- Call 911, even if symptoms improve.
- Lie flat with legs raised (sit up if breathing is hard). Give a second dose after 5–15 minutes if there is no improvement.
Antihistamines and steroids do not treat anaphylaxis and must never delay epinephrine. Carry two doses and follow the written emergency action plan from your allergist.
Management of Cashew Allergy
Avoidance Strategies
- Read Labels: Cashews are found in trail mixes, nut butters, vegan cheeses.
- Cross-Contamination: Often processed with pistachios and almonds.
Emergency Treatment
- Epinephrine (auto-injector or nasal spray) for severe reactions.
- Antihistamines may ease mild skin symptoms such as itching or hives, but they do not treat anaphylaxis and must never delay epinephrine.
- Corticosteroids are sometimes given by doctors after a reaction, but they do not treat anaphylaxis and have not been shown to prevent a second-wave (biphasic) reaction.
Immunotherapy (OIT)
- Experimental desensitization therapy is being researched.
Conclusion
- Cashews contain potent allergens (Ana o 1, Ana o 2, Ana o 3), causing severe IgE-mediated reactions.
- Cross-reactivity is highest with pistachio: most people allergic to cashew also react to pistachio (and vice versa), so avoid pistachio unless an allergist confirms it is tolerated. Peanut and walnut allergy often occur alongside cashew allergy but are usually separate sensitizations.
- Cooking does not reduce allergenicity.
- Anaphylaxis risk → Patients must carry epinephrine.