Are cashews poisonous?

Are Cashews Poisonous?

Cashews themselves are not poisonous when properly processed and consumed as the edible kernel, but raw cashew nut shells contain toxic resorcinol allergens (cardol and anacardic acid) that can cause severe dermatitis, and the cashew kernel is a potent food allergen capable of triggering life-threatening anaphylaxis in sensitized individuals. 1, 2, 3

Two Distinct Safety Concerns with Cashews

1. Chemical Toxicity from Shell Oil (Contact Dermatitis)

Raw cashew nut shells contain cardol and anacardic acid—resorcinol allergens chemically similar to poison ivy urushiol—that cause severe contact dermatitis when touched or ingested. 2, 3

• The dermatitis typically appears 1-3 days after exposure to contaminated raw cashews, presenting as a pruritic, erythematous, maculopapular eruption with flexural accentuation on extremities, groin, and buttocks 2, 3
• Mass spectrometry has confirmed the presence of cardol in cashew shell oil extracts 3
• Commercially available cashews are roasted or steamed to remove these toxic shell oils, making them safe for consumption from a toxicity standpoint 3
• Cross-reactivity exists between cashew shell allergens and poison ivy (Toxicodendron) 2

Critical pitfall: Imported or improperly processed cashews may be contaminated with shell oil residue, causing unexpected dermatitis outbreaks 3

2. IgE-Mediated Food Allergy (Anaphylaxis Risk)

Cashew nut is classified as a potent allergenic food that triggers severe, systemic immune reactions including anaphylaxis in sensitized individuals, often requiring epinephrine treatment and hospitalization. 1, 4

Severity Compared to Other Tree Nuts

Cashew allergy causes more severe reactions than peanut allergy, with significantly higher rates of respiratory and cardiovascular symptoms. 4

• In a case-matched study of 141 children, cashew reactions showed:
  • 8.4 times higher odds of wheezing (OR: 8.4,95% CI: 3.2-22.0) 4
  • 13.6 times higher odds of cardiovascular symptoms (OR: 13.6,95% CI: 5.6-32.8) 4
  • 13.3 times higher odds of requiring intramuscular epinephrine (OR: 13.3,95% CI: 5.5-32.2) 4
  • 25.1 times higher odds of severe reactions with dyspnea or collapse (OR: 25.1,95% CI: 3.1-203.5) 4

Major Allergens Identified

The dominant IgE-binding allergens in cashew include Ana o 1 and Ana o 2 (13S globulin/legumin-like proteins in the 31-35 kDa range) and Ana o 3 (2S albumin family), all classified as major allergens. 1, 5

Risk Factors for Severe Reactions

Asthma is the most significant risk factor for severe allergic reactions to cashew and other tree nuts. 6

• Concomitant asthma, especially severe asthma with adrenal suppression from chronic glucocorticoid therapy, increases risk of near-fatal or fatal reactions 7
• Atopic dermatitis within the first 6 months of life is associated with increased risk of developing tree nut allergies 6
• Children with existing food allergies have 4 times higher odds of having asthma, which can increase the severity of anaphylactic reactions 6

Cross-Reactivity Concerns

Patients with cashew allergy should be evaluated for potential cross-reactivity with pistachio and other tree nuts due to the high likelihood of multiple tree nut allergies. 6

• Approximately 30.4% of children with food allergies have multiple food allergies, which may include cross-reactive tree nuts 6
• Skin prick tests and specific IgE testing should be performed to evaluate potential cross-reactivity between cashew and other tree nuts 6

Management of Cashew Allergy

Patients with cashew allergy should be prescribed two epinephrine autoinjectors due to the high risk of severe reactions. 6

• The severity of cashew allergy cannot be reliably predicted by the magnitude of skin or blood test results 6
• Delayed administration of epinephrine has been implicated in contributing to fatalities from tree nut-induced anaphylaxis 6
• Patients should be observed for 4-6 hours after treatment for cashew-induced anaphylaxis, as biphasic reactions can occur in 1-20% of cases 6

There is currently no cure for cashew nut allergy; allergic patients are advised to eliminate it from their diets and rely on proper food labeling when choosing processed foods. 1