Pistachio

Diagnostic Skin Prick Testing

For adults, the standard procedure involves applying one drop of the non-standardized Pistachio extract (usually at a 1:10 or 1:20 w/v concentration) to the forearm or back. A sterile lancet is used to prick the skin through the drop. A positive control (histamine) and a negative control (saline) are used simultaneously. The results are read after 15 to 20 minutes. A wheal diameter 3mm greater than the negative control is typically considered a positive result.

Oral Immunotherapy (OIT)

In experimental or specialized clinical settings, adult OIT begins with an 'Initial Escalation Phase' where doses may start as low as 0.1 mg of Pistachio protein. This is followed by a 'Build-up Phase' where the dose is increased every 2 weeks over several months until a maintenance dose (often 300 mg to 1000 mg) is reached. Maintenance must be continued daily to maintain desensitization.

Diagnostic Testing

Pediatric dosing for skin testing is identical to adult dosing in terms of concentration, though fewer test sites may be used on the back of infants to avoid discomfort.

Oral Immunotherapy (OIT)

Pistachio OIT is most commonly performed in children aged 4 to 17. The dosing schedule is highly individualized. According to recent clinical trials (e.g., the PALISADE and ARTEMIS frameworks for other nuts), the goal is to reach a maintenance dose that protects against accidental ingestion of 1-2 whole pistachios.

Renal Impairment

No specific dosage adjustments are required for renal impairment when using allergenic extracts, as systemic exposure is minimal. However, in parenteral lipid emulsions, renal function should be monitored to ensure clearance of metabolic byproducts.

Hepatic Impairment

Caution is advised when using lipid emulsion forms in patients with severe hepatic impairment or cholestasis, as lipid metabolism may be impaired. For allergenic extracts, no adjustment is necessary.

Elderly Patients

Elderly patients may have reduced skin reactivity (reduced histamine response), which can lead to false-negative results in diagnostic testing. Clinicians may need to interpret results more conservatively.

For Skin Testing

• The test must be performed in a clinical setting equipped with emergency resuscitation equipment (epinephrine).
• The skin site must be clean and free of dermatitis.
• Avoid taking antihistamines for at least 3-7 days prior to the test.

For Oral Immunotherapy

• The dose must be taken at the same time every day.
• The dose should be mixed with a non-heated vehicle food (like applesauce or yogurt).
• Do not take the dose on an empty stomach.
• Do not exercise, take hot showers, or consume alcohol for 2-3 hours after the dose, as these factors can lower the reaction threshold (augmentation factors).

In OIT, if a single dose is missed, take the next dose as scheduled. Do not double the dose. If two or more consecutive doses are missed, contact your allergist immediately, as a dose reduction or 're-escalation' may be necessary to prevent a systemic reaction.

An overdose of Pistachio extract in the context of OIT or skin testing manifests as a systemic allergic reaction (anaphylaxis). Symptoms include hives, swelling of the throat, wheezing, and a drop in blood pressure. Immediate administration of intramuscular epinephrine is required. In the case of lipid emulsion overdose, 'fat overload syndrome' may occur, characterized by hyperlipidemia, fever, and liver dysfunction.

> Important: Follow your healthcare provider's dosing instructions. Do not adjust your dose without medical guidance.

In the context of diagnostic testing and Oral Immunotherapy (OIT), the following side effects are very common:

• Localized Pruritus (Itching): Intense itching at the site of the skin prick or, in OIT, itching of the mouth and throat (Oral Allergy Syndrome).
• Wheal and Flare: A raised, red bump at the testing site, similar to a mosquito bite, which typically resolves within 2 to 4 hours.
• Abdominal Pain: Cramping or discomfort in the stomach area as the immune system in the gut reacts to the protein.
• Nausea: A feeling of sickness in the stomach, often occurring shortly after an oral dose.

• Urticaria (Hives): Itchy red welts that may appear on areas of the body distant from the administration site.
• Vomiting: Occasional emesis following an oral dose, particularly during the build-up phase of OIT.
• Rhinitis: Runny or stuffy nose and sneezing.
• Eosinophilic Esophagitis (EoE): Chronic inflammation of the esophagus, characterized by difficulty swallowing (dysphagia) or food impaction. This is a known risk of long-term OIT.

• Angioedema: Deep tissue swelling, most commonly affecting the lips, eyelids, or tongue.
• Hypotension: A dangerous drop in blood pressure, often associated with anaphylaxis.
• Fat Overload Syndrome: Specifically related to intravenous lipid emulsions, involving sudden elevation of serum triglycerides and hepatosplenomegaly (enlarged liver and spleen).

> Warning: Stop taking Pistachio and call your doctor immediately if you experience any of these.

• Anaphylaxis: A systemic, life-threatening allergic reaction. Symptoms include a 'sense of impending doom,' swelling of the airway, difficulty breathing, and fainting.
• Severe Bronchospasm: Sudden constriction of the airways, making it nearly impossible to breathe, particularly in patients with pre-existing asthma.
• Chest Pain or Tightness: May indicate a cardiovascular stress response to a systemic reaction.
• Persistent Vomiting or Diarrhea: Can lead to dehydration and may be a sign of a progressing systemic allergic response.

The primary long-term concern with Pistachio allergenic extract use, specifically in OIT, is the development of Eosinophilic Esophagitis (EoE). Studies suggest that approximately 2-5% of patients undergoing food OIT may develop EoE, which often necessitates the discontinuation of the therapy. Symptoms of EoE may not appear for months or years after starting treatment. Additionally, there is the risk of 'loss of desensitization' if the daily maintenance dose is not strictly followed, potentially leading to a return of severe sensitivity.

While non-standardized extracts often carry general warnings, the FDA requires a Black Box Warning for many allergenic extracts (such as those used in sublingual or oral immunotherapy) regarding the risk of Severe Anaphylaxis.

Summary of Warning: Pistachio allergenic extracts can cause life-threatening allergic reactions, including anaphylaxis. Patients must be monitored for at least 30 minutes following skin testing or initial dose escalation. Patients must be prescribed and trained in the use of an epinephrine auto-injector to keep with them at all times while undergoing treatment. Treatment should not be initiated in patients with unstable or poorly controlled asthma.

Report any unusual symptoms to your healthcare provider.

Pistachio allergenic extracts must only be administered by healthcare professionals experienced in the diagnosis and treatment of allergic diseases. The facility must be equipped with 'crash carts' containing oxygen, IV fluids, and emergency medications like epinephrine, antihistamines, and corticosteroids. Patients should be informed that a negative skin test does not always rule out a clinical allergy, and a positive test does not always mean a patient will react to eating the nut; clinical history is paramount.

No FDA black box warnings exist specifically for the non-standardized Pistachio extract vial itself, but the class of allergenic immunotherapy products carries a rigorous warning regarding Anaphylaxis Risk. The warning emphasizes that systemic reactions can occur even in patients who have previously tolerated the extract and that the risk is higher in those with comorbid asthma or those taking certain medications like beta-blockers.

• Allergic Reactions / Anaphylaxis Risk: This is the primary risk. The reaction can be unpredictable. Patients must be observed for a minimum of 30 minutes post-administration.
• Asthma Status: Patients with uncontrolled asthma are at a significantly higher risk for fatal anaphylaxis. Asthma must be stabilized (FEV1 >80% predicted) before any diagnostic testing or OIT escalation.
• Infection/Illness: During OIT, if a patient has a viral infection or fever, the dose should be held or reduced, as illness can lower the threshold for a systemic allergic reaction.
• Exercise and Heat: Physical exertion, hot baths, or saunas within 3 hours of an OIT dose can increase the rate of absorption and trigger a reaction (exercise-induced anaphylaxis).

• Spirometry: Recommended for patients with asthma before starting therapy.
• Serum IgE and Skin Prick Tests: Monitored annually to assess the progress of desensitization.
• Liver Function Tests (LFTs): Required if using Pistachio-derived lipids in parenteral nutrition to monitor for TPN-associated liver disease.
• Triglyceride Levels: Monitored in patients receiving lipid emulsions to prevent fat overload syndrome.

Pistachio extract itself does not cause sedation. However, if an allergic reaction occurs or if the patient takes an antihistamine (like diphenhydramine) to treat a mild reaction, they should not drive or operate heavy machinery due to the risk of drowsiness.

Alcohol consumption is strictly contraindicated for at least 3 hours after an OIT dose. Alcohol increases gastrointestinal permeability and vasodilation, which can significantly increase the risk of a systemic allergic reaction.

Discontinuing Pistachio OIT must be done under medical supervision. If the maintenance dose is stopped abruptly, the patient will lose their desensitization within days to weeks, placing them at high risk for anaphylaxis if they accidentally ingest pistachios.

> Important: Discuss all your medical conditions with your healthcare provider before starting Pistachio.

• Beta-Blockers (e.g., Propranolol, Metoprolol): These medications are contraindicated during allergenic extract testing and OIT. Beta-blockers can make an allergic reaction more severe and, more importantly, can render epinephrine (the life-saving treatment for anaphylaxis) ineffective by blocking the beta-receptors that epinephrine needs to stimulate.

• ACE Inhibitors (e.g., Lisinopril, Enalapril): These drugs may interfere with the body's compensatory mechanisms during anaphylaxis (such as the renin-angiotensin system), potentially leading to more severe hypotension (low blood pressure) during a reaction.
• MAO Inhibitors (e.g., Phenelzine): Can potentiate the effects of sympathomimetic amines used to treat reactions, leading to hypertensive crisis.

• Antihistamines (H1-blockers like Loratadine, Cetirizine): These medications must be stopped 3 to 7 days before skin testing because they suppress the histamine-induced wheal and flare, leading to false-negative results. They do not, however, interfere with the underlying allergic sensitization.
• Tricyclic Antidepressants (e.g., Amitriptyline): These can have potent antihistamine effects and may interfere with diagnostic testing results.

• Cross-Reactive Foods: Patients allergic to Pistachio often show cross-reactivity with Cashews and Mangoes (specifically mango skin) due to shared proteins (ana o 1 and pis v 1). Consuming these foods during Pistachio OIT may increase the total 'allergen load' and trigger a reaction.
• High-Fat Meals: May slow the absorption of OIT doses but could also increase the total amount of protein absorbed in some individuals. Consistency in meal composition is key.

• St. John's Wort: While no direct interaction with the extract exists, its potential to affect drug metabolism may complicate the treatment of systemic reactions.
• Feverfew or Ginkgo Biloba: These may have anti-platelet effects; while not directly interacting with the allergen, they could theoretically complicate the management of severe systemic inflammation.

• Skin Prick Tests: As mentioned, antihistamines and certain antidepressants will cause false negatives.
• Serum Specific IgE (ImmunoCAP): Pistachio extracts do not interfere with this blood test, as it is performed in vitro (in a lab) rather than on the patient's skin.

> Important: Tell your doctor about ALL medications, supplements, and herbal products you are taking.

• Severe, Uncontrolled Asthma: Patients with an FEV1 <80% of predicted or those who have had a recent asthma exacerbation must not undergo testing or OIT, as they are at the highest risk for fatal respiratory failure during an allergic reaction.
• Recent Myocardial Infarction (Heart Attack): Within the last 3-6 months. The physiological stress of a potential anaphylactic reaction and the subsequent need for epinephrine (which increases heart rate and oxygen demand) pose an unacceptable risk.
• History of Eosinophilic Esophagitis (EoE): Patients with a pre-existing diagnosis of EoE should not undergo OIT, as the therapy is known to exacerbate this condition.
• Hypersensitivity to Diluents: Some extracts contain phenol or glycerin. Patients with a known severe allergy to these stabilizers should not be tested with these specific formulations.

• Pregnancy: While not an absolute contraindication for continuing a maintenance dose, initiating Pistachio OIT or performing skin testing during pregnancy is generally avoided due to the risk of maternal anaphylaxis, which can cause fetal hypoxia (lack of oxygen).
• Autoimmune Disorders: Patients with active systemic autoimmune diseases may have unpredictable immune responses to immunotherapy.
• Beta-Blocker Therapy: If the patient cannot be safely transitioned to an alternative antihypertensive, the risks of immunotherapy may outweigh the benefits.

Patients should be aware of 'Botanical Cross-Sensitivity.' Pistachios are in the family Anacardiaceae. There is a high degree of cross-reactivity with:

1. 1Cashews: Over 90% of pistachio-allergic patients are also cashew-allergic.
2. 2Mangoes: Specifically the skin/peel, which contains urushiol-like compounds.
3. 3Poison Ivy/Sumac: Also members of the same family; patients may experience more severe contact dermatitis.

> Important: Your healthcare provider will evaluate your complete medical history before prescribing Pistachio.

Pregnancy Category C: No adequate and well-controlled studies have been conducted in pregnant women. The primary risk is not the Pistachio extract itself, but the potential for anaphylaxis. If a pregnant woman experiences anaphylaxis, the resulting drop in blood pressure can cause a critical reduction in placental blood flow, leading to fetal distress, neurological injury, or death. Therefore, skin testing or starting OIT is typically postponed until postpartum. If a patient is already on a stable maintenance dose of OIT, many allergists recommend continuing the dose, as the risk of a reaction from accidental ingestion is higher than the risk of a reaction from a controlled dose.

It is not known whether Pistachio allergenic proteins are excreted in human milk in quantities that would affect a nursing infant. However, maternal IgE does not pass into breast milk, but maternal IgG4 (the protective antibody) does. Most clinicians consider it safe to continue Pistachio immunotherapy while breastfeeding, provided the mother is monitored for reactions.

Pistachio OIT is primarily studied in the pediatric population (ages 4-17). Children often have more robust immune responses and higher rates of desensitization success compared to adults. However, they also require stricter supervision to ensure they do not engage in high-intensity exercise or take hot showers following their dose. The safety of Pistachio extracts in children under age 4 has not been formally established for OIT, though skin testing is performed at any age.

Clinical trials for Pistachio allergenic extracts generally do not include sufficient numbers of subjects aged 65 and over. In older adults, the risk of cardiovascular complications from a systemic reaction is significantly higher. Additionally, skin reactivity decreases with age, which may necessitate the use of intradermal testing if skin prick results are ambiguous, though intradermal testing for food allergens is generally avoided due to the high risk of anaphylaxis.

For allergenic extracts used in diagnosis or OIT, no dosage adjustment is required for patients with renal impairment. For lipid emulsions containing pistachio oil, clinicians should monitor for the accumulation of nitrogenous waste and ensure the patient's fluid status is managed, as these patients may be at risk for metabolic acidosis.

In patients with chronic liver disease, the synthesis of proteins and the metabolism of lipids are impaired. If using lipid emulsions, these patients are at high risk for PNALD (Parenteral Nutrition Associated Liver Disease). Dose reduction and frequent monitoring of bilirubin and liver enzymes are mandatory.

> Important: Special populations require individualized medical assessment.

Pistachio allergenic extract works by presenting specific protein antigens to the immune system. The major allergens identified in Pistacia vera are:

• Pis v 1: A 2S albumin (storage protein).
• Pis v 2: An 11S legumin.
• Pis v 3: A 7S vicilin.

In diagnostic testing, these proteins cross-link IgE on mast cells. In immunotherapy, the mechanism involves 'Peripheral Tolerance.' This is achieved by increasing the frequency of T-regulatory (Treg) cells (CD4+CD25+Foxp3+), which secrete IL-10 and TGF-beta. These cytokines suppress the Th2 response (which produces IgE) and promote the production of IgG4. IgG4 acts as a 'blocking antibody,' competing with IgE for the allergen binding sites, thereby preventing mast cell degranulation.

The onset of the diagnostic effect (wheal and flare) occurs within 5-10 minutes and peaks at 15-20 minutes. The duration of the desensitization effect in OIT is transient; if the daily dose is stopped, the 'threshold' for an allergic reaction begins to drop within 48-72 hours. This demonstrates that OIT induces desensitization (a temporary state) rather than tolerance (a permanent change) in most patients.

| Parameter | Value |

|---|---|

| Bioavailability | High for proteins in OIT; Low for skin testing |

| Protein Binding | N/A (Proteins are metabolized) |

| Half-life | Proteins: Minutes to Hours; IgG4: 21 days |

| Tmax | 15-20 minutes (Skin Test) |

| Metabolism | Proteolysis (Proteases) |

| Excretion | Renal (Amino acid metabolites) |

Pistachio extracts are complex mixtures of proteins, lipids, and carbohydrates. The primary allergenic proteins are heat-stable and resistant to pepsin digestion, which explains their potency as food allergens. The molecular weights of the major allergens range from 7 kDa (Pis v 1) to 52 kDa (Pis v 3). The extract is typically clear to slightly turbid and may have a yellowish tint due to natural oils.

Pistachio belongs to the Non-Standardized Food Allergenic Extract class. It is closely related to other tree nut extracts like Cashew, Walnut, and Almond. Within the Lipid Emulsion class, it is grouped with soybean oil, safflower oil, and olive oil emulsions used in clinical nutrition.