Table of Contents

What Inside a Peanut Triggers Allergies?

Key Takeaways

Peanut allergy is caused by specific peanut proteins, mainly Ara h 1, Ara h 2 and Ara h 3.
Ara h 2 is strongly linked with severe reactions, including anaphylaxis.
Diagnosis uses skin prick tests, blood tests for peanut-specific IgE and supervised oral food challenges.
Early introduction of peanut in infancy may reduce allergy risk, as shown by landmark research.
Roasting can increase the allergenicity of peanut proteins.
Carrying an adrenaline autoinjector and having a clear emergency plan are essential for people at risk.
First aid for anaphylaxis must be administered immediately; call emergency services.
Food labelling laws in Australia require clear declaration of peanuts on packaged foods.

Peanut allergy is one of the most common and potentially serious food allergies, especially in Australia where prevalence has risen over recent decades. This guide explains which components in peanuts trigger allergic reactions, how the immune system responds, risk factors for developing the allergy, diagnostic methods, and current approaches to treatment and prevention.

Understanding Peanut Allergy: A Brief Overview

A peanut allergy happens when the immune system wrongly treats certain peanut proteins as harmful. This triggers an exaggerated immune response that can range from mild symptoms, such as hives, to severe, life-threatening anaphylaxis. This section outlines the mechanisms and the key proteins involved.

What Is a Food Allergy?

A food allergy is an immune system response to a food protein that the body mistakenly regards as a threat. This differs from food intolerance, which typically involves digestive symptoms and does not involve the immune system. Food allergies can be life-threatening and usually require stricter management.

Prevalence of Peanut Allergy in Australia

Peanut allergy affects a notable proportion of children in Australia. Some children outgrow their allergy, but many remain allergic into adulthood. Rising rates have made peanut allergy a significant public health issue and a focus for research in prevention and treatment.

Major Peanut Proteins That Trigger Allergies

Peanuts contain multiple proteins that can trigger allergic responses. Scientists identify the main allergens using the Ara h nomenclature (Ara h 1 to Ara h 9). The most clinically important proteins are described below.

Ara h 1, Ara h 2 and Ara h 3 — Major Allergens

These are seed storage proteins present in peanuts.
They are very stable and resist breakdown during digestion and cooking.
Ara h 2 is especially associated with severe allergic reactions and is a strong predictor of anaphylaxis risk.

Ara h 8 and Ara h 9 — Cross-Reactivity and Pollen-Food Syndrome

Ara h 8 can cross-react with birch pollen proteins, so people with birch pollen allergy may react to peanuts.
Ara h 9 can cause cross-reactivity with certain fruits and nuts, and is more relevant where pollen-food syndrome occurs.

How the Immune System Responds to Peanut Allergens

The Role of IgE Antibodies

In people with peanut allergy, the immune system produces IgE antibodies specific to peanut proteins. These antibodies bind to mast cells and basophils, sensitising them.

Histamine and Allergic Symptoms

When the body encounters the peanut protein again, the sensitised cells release mediators such as histamine, producing symptoms like:

Swelling and itching
Hives
Wheeze and breathing difficulty
Vomiting
In severe cases, anaphylaxis

Risk Factors: Why Do Some People Become Allergic?

Genetic and Family History

A family history of allergies, asthma or eczema increases the risk of developing peanut allergy. Genetics plays an important role in susceptibility.

Environmental and Dietary Factors

Hygiene hypothesis: reduced early microbial exposure may predispose immune systems to overreact.
Early introduction versus avoidance: studies such as LEAP suggest early introduction of peanut between 4 and 11 months can reduce allergy risk in high-risk infants.
Gut microbiota: emerging evidence suggests the gut microbiome influences allergy development.

How Peanut Allergens Are Detected and Diagnosed

Common diagnostic methods include:

Skin prick testing
Blood tests measuring peanut-specific IgE
Oral food challenges conducted under medical supervision

Component-Resolved Diagnostics (CRD)

CRD tests determine sensitisation to specific proteins such as Ara h 2, improving prediction of reaction severity and helping guide management decisions.

Can Peanut Allergens Be Removed or Altered?

Roasting and Allergen Stability

Roasting can make certain peanut proteins more stable and more allergenic compared with raw or boiled peanuts. This helps explain why roasted peanuts often provoke stronger reactions.

Genetically Modified Peanuts

Research is exploring hypoallergenic peanuts produced by altering or silencing genes that code for allergenic proteins. These approaches are experimental and raise technical, regulatory and ethical questions.

Living with Peanut Allergy: Practical Guidance

Food Labelling Laws in Australia

Australian regulations require clear labelling of priority allergens, including peanuts. Always read labels carefully and be aware of possible cross-contamination warnings.

Workplace and Social Considerations

Inform employers and anyone responsible for food preparation about the allergy.
Promote clear food handling practices in shared spaces.
Carry emergency medication such as an adrenaline autoinjector (for example, EpiPen) and ensure others know how to use it.
Consider medical identification, such as a medical bracelet, to alert responders in an emergency.

First Aid for Peanut Allergy and Anaphylaxis (CPR-first aid focus)

This practical section ties into first aid priorities and CPRFIRSTAID’s scope.

Emergency response checklist for suspected anaphylaxis

Call emergency services immediately.
Administer adrenaline using an autoinjector without delay if anaphylaxis is suspected.
Lay the person flat and keep them warm unless breathing difficulty requires sitting up.
Repeat adrenaline after 5 minutes if symptoms do not improve and a second autoinjector is available.
Use CPR if the person loses consciousness and stop breathing. Trained responders should follow resuscitation protocols.
Always seek urgent medical review after any adrenaline administration.

Prevention and preparedness

Ensure staff at work and carers are trained in recognising anaphylaxis and using an autoinjector.
Keep an anaphylaxis action plan accessible.
Run regular drills if you manage a setting with children or vulnerable adults.

Current and Future Treatments

Oral Immunotherapy and Desensitisation

OIT introduces increasing doses of peanut protein to build tolerance. It shows promise but can carry risks and is typically offered in specialist centres or clinical trials.

Vaccines and Biologics

Research into vaccines and biologic therapies, including monoclonal antibodies that block allergic pathways, is ongoing. These may provide new options in future.