Pistacia vera (Anacardiaceae)

Botanical Characteristics of Pistachio (Pistacia vera)

• Scientific Name: Pistacia vera
• Family: Anacardiaceae (Cashew family)
• Common Names: Pistachio, Green Nut
• Native Region: Middle East and Central Asia

Tree and Nut Description

• Pistachio trees are deciduous and grow 5–10 meters tall.
• The seeds (pistachios) are enclosed in a hard shell, which naturally splits open when ripe.
• Pistachios are closely related to cashews and mangoes, as they belong to the Anacardiaceae family.

Pistachio as a Food Allergen

Pistachios are classified as a major food allergen by the U.S. FDA, requiring mandatory labeling due to documented IgE-mediated hypersensitivity reactions.

Allergenic Proteins in Pistachios

Allergen Name	Protein Family	Molecular Weight (kDa)	Function	Cross-Reactivity
Pis v 1	11S Globulin (Legumin)	~40 kDa	Storage protein	Cross-reacts with cashews, walnuts, almonds
Pis v 2	7S Vicilin	~50 kDa	Storage protein	Similar to peanuts, hazelnuts
Pis v 3	2S Albumin	~9 kDa	Seed storage protein	Cross-reacts with cashews, Brazil nuts
Pis v 4	Lipid Transfer Protein (LTP)	~9 kDa	Defense protein	Linked to peach, apple, cherry allergies
Pis v 5	Profilin	~15 kDa	Actin-binding protein	Cross-reacts with birch pollen, grass pollen

Cross-Reactivity

• Pistachios have high cross-reactivity with cashews (both belong to the Anacardiaceae family).
• Similar allergenic proteins to walnuts, almonds, and peanuts due to shared Vicilin and Legumin proteins.
• Pistachio LTP (Pis v 4) may cross-react with Rosaceae fruits (peach, apple, cherry).
• Profilin allergens (Pis v 5) may cause mild symptoms in pollen-allergic individuals.

Epitope Mapping of Pistachio Allergens

Pistachio allergens contain linear and conformational IgE-binding epitopes.

Pis v 1 (11S Globulin – Legumin)

• Regions with IgE-binding epitopes:
  • Amino acids: 50–70, 120–140, 200–220
  • Core IgE-binding sites: Beta-sheet hydrophobic domains
• Clinical Significance:
  • Highly stable, resistant to digestion.
  • Cross-reacts with walnuts, almonds, and cashews.
  • Main cause of severe allergic reactions in tree nut–allergic individuals.

Pis v 2 (7S Vicilin)

• Regions with IgE-binding epitopes:
  • Amino acids: 30–50, 100–120, 170–190
  • Core IgE-binding sites: Beta-barrel structures
• Clinical Significance:
  • Common allergen in tree nuts and legumes.
  • Similar to peanut (Ara h 1) and hazelnut proteins.
  • Moderate resistance to digestion.

Pis v 3 (2S Albumin)

• Regions with IgE-binding epitopes:
  • Amino acids: 10–30, 90–110, 140–160
  • Core IgE-binding sites: Cysteine-stabilized domains
• Clinical Significance:
  • Highly stable allergen, causing severe allergic reactions.
  • Cross-reacts with cashews, Brazil nuts.
  • Resistant to heat and enzymatic breakdown.

Pis v 4 (Lipid Transfer Protein – LTP)

• Regions with IgE-binding epitopes:
  • Amino acids: 20–40, 80–100, 130–150
  • Core IgE-binding sites: Hydrophobic lipid-binding regions
• Clinical Significance:
  • Triggers severe reactions in LTP-sensitive individuals.
  • Cross-reacts with peaches, apples, cherries (Rosaceae family).

Pis v 5 (Profilin)

• Regions with IgE-binding epitopes:
  • Amino acids: 30–50, 100–120
  • Core IgE-binding sites: Actin-binding domains
• Clinical Significance:
  • Mild allergen, often linked to Oral Allergy Syndrome (OAS).
  • Cross-reacts with birch pollen, grass pollen.

Stability of Pistachio Allergens

Allergen	Heat Stability	Gastric Stability	Processing Effect
Pis v 1 (11S Globulin)	High	High	Resistant to roasting
Pis v 2 (7S Vicilin)	Medium	Medium	Partially degraded
Pis v 3 (2S Albumin)	High	High	Survives processing
Pis v 4 (LTP)	High	High	Stable even in refined nut oils
Pis v 5 (Profilin)	Low	Low	Destroyed by cooking

• Pistachio allergens like Pis v 1 and Pis v 3 remain stable, meaning roasted pistachios can still cause reactions.
• Profilins are heat-sensitive and may be reduced in cooked or processed foods.

Symptoms of Pistachio Allergy

Reactions range from mild to life-threatening.

Mild Symptoms

• Oral Allergy Syndrome (OAS): Itchy mouth, tingling lips.
• Hives, skin rash.
• Nausea, vomiting, diarrhea.

Severe Symptoms (Anaphylaxis)      Epinephrine (EpiPen®) is required for anaphylaxis.

• Swelling of throat (laryngeal edema).
• Difficulty breathing, wheezing.
• Drop in blood pressure (anaphylactic shock).

Diagnosis and Testing

Skin Prick Test (SPT)

• Detects IgE-mediated reactions to pistachio extract.

Serum IgE Testing

• Measures IgE antibodies against Pis v 1, Pis v 2, Pis v 3.

Oral Food Challenge (OFC)

• Gold standard for confirming allergy.
• Performed under medical supervision.

Comparison with Other Tree Nuts

Nut	Major Allergen	Cross-Reactivity	Stability	Anaphylaxis Risk
Pistachio	Pis v 1, Pis v 2, Pis v 3	Cashews, Walnuts, Almonds	High	High
Cashew	Ana o 1, Ana o 2, Ana o 3	Pistachios, Walnuts	High	High
Hazelnut	Cor a 1, Cor a 9, Cor a 11	Birch Pollen, Tree Nuts	Moderate	Moderate

• Pistachios are most closely related to cashews, making cross-reactivity highly likely.
• Strong IgE-binding allergens make pistachio a significant allergen risk.