Palforzia Side Effects: What to Expect and When to Call Your Doctor

Because Palforzia works by exposing your child to the very allergen they are sensitive to — peanut protein — side effects are not just possible, they are expected, especially during early dosing phases. The key is knowing which side effects are manageable reactions that typically pass, and which are warning signs that require immediate medical attention. This guide explains everything parents and patients need to know.

The Boxed Warning: Anaphylaxis Risk

Palforzia carries a

Boxed Warning — the FDA's strongest safety warning — for the risk of anaphylaxis. Anaphylaxis is a severe, potentially life-threatening allergic reaction that can occur at any time during Palforzia therapy, including during home doses. This is why the FDA required the REMS program: to ensure that every patient has an epinephrine auto-injector available at all times and that healthcare providers are trained to respond to reactions.

Every patient on Palforzia must have injectable epinephrine — such as an EpiPen or Auvi-Q — available at all times. This is non-negotiable and is part of the REMS program requirements.

Common Side Effects of Palforzia (Expected and Usually Manageable)

The most common side effects occur especially during early up-dosing phases and tend to improve as the body adjusts. In clinical trials, common adverse reactions in patients ages 4-17 included:

Abdominal pain and stomach cramping

Nausea and vomiting

Oral pruritus (itchy mouth or throat)

Oral paresthesia (tingling in the mouth)

Throat irritation and throat tightness

Cough and wheezing

Rhinorrhea (runny nose) and sneezing

Urticaria (hives) and pruritus (skin itching)

Ear pruritus (itchy ears)

Dyspnea (shortness of breath)

In younger patients (ages 1-3), common reactions also included cough, sneezing, rhinitis, nasal congestion, and perioral dermatitis (skin irritation around the mouth).

When Side Effects Are Most Likely: The Dosing Phases

Side effects are most common and can be most intense during:

Initial Dose Escalation (clinic day): Every escalating dose (0.5mg → 1mg → up to 6mg) is given 20-30 minutes apart; observed for at least 60 minutes after the final dose. Reactions here are managed immediately by trained clinical staff.

First dose of each Up-Dosing level (at clinic): Every time the dose increases to a new level — including the 3 mg level — it is given in-clinic with at least 60 minutes of observation.

Daily home doses: Reactions can occur with any home dose. Your child should remain at home — not exercising, not ill, not fasting — for at least 30-60 minutes after taking their daily dose.

Serious Side Effects: Call 911 Immediately

These symptoms are signs of anaphylaxis and require emergency epinephrine and immediate 911 activation:

Severe throat tightness or throat closing sensation

Difficulty breathing or severe wheezing

Rapid drop in blood pressure (feeling faint or collapsing)

Loss of consciousness

Pale or bluish skin color

Rapid or weak pulse

If your child shows any of these signs, use epinephrine immediately and call 911. Do NOT wait to see if symptoms improve on their own.

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Eosinophilic Esophagitis (EoE): A Serious Complication to Watch For

Eosinophilic esophagitis (EoE) is a serious inflammatory condition of the esophagus that can develop during Palforzia therapy. It is different from an acute allergic reaction — it develops gradually. Symptoms include:

Difficulty or pain when swallowing (dysphagia)

Food getting stuck in the throat or esophagus

Chest pain or heartburn that doesn't respond to antacids

Vomiting (recurring)

If your child develops these symptoms, contact your allergist promptly. Palforzia must be discontinued in patients with a history of EoE, and the prescribing label contraindicates Palforzia for patients with prior EoE diagnoses.

Factors That Increase Reaction Risk

Palforzia reactions are more likely when your child:

Takes the dose on an empty stomach (always take Palforzia with a meal or snack)

Is sick with a viral illness or has an asthma exacerbation

Exercises vigorously within 2-3 hours of taking a dose

Has poorly controlled asthma (Palforzia is contraindicated in uncontrolled asthma)

Is in the first few days of a new, higher dose level

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Finding Help If You Have Questions About Reactions

Your first resource for questions about Palforzia side effects is always your child's REMS-certified allergist. For questions about the ongoing supply situation, read our Palforzia shortage update for patients for the latest on availability and transition planning.