What Is Peanut Allergy

Introduction

A peanut allergy is a type of food allergy characterized by an abnormal immune response to proteins found in peanuts.¹ When an individual with a peanut allergy comes into contact with peanuts or peanut-containing products, their immune system mistakenly identifies these proteins as harmful invaders and triggers an immune response to defend the body.² This immune response can lead to mild to moderate allergic symptoms such as itching, swelling, hives, diarrhoea, and, in severe cases, anaphylaxis, which can be life-threatening. This allergy has become a pressing public health concern, affecting millions of individuals worldwide, primarily children. Understanding peanut allergies is crucial not only for those affected but also for society at large, as it impacts the way we approach food labelling, allergy education, and overall public health.³

Peanut allergy: an overview

A peanut allergy is a type of food allergy characterized by an abnormal immune response to proteins found in peanuts.¹ Peanuts are legumes that grow underground and are different from tree nuts. Therefore, the allergy caused by peanuts is different than tree nut allergies. Infants who suffer from egg allergy or eczema are at a higher risk of developing this allergy.⁴ It starts to develop in early childhood, but it can also appear in adulthood. Some children may outgrow it, but for some, it may persist. If someone has a peanut allergy, they have a higher chance of developing an allergy to sesame and lupin.³

Symptoms of peanut allergy

The symptoms of allergy can show within a few minutes or an hour after any contact with peanuts. The reactions can range from mild to moderate or severe.³

Mild to moderate symptoms

These include:

• Itchiness in mouth, tongue and throat
• Swelling of lips, around the eyes or face
• Red raised itchy rash (called hives or urticaria)
• Vomiting
• Nausea
• Abdominal pain 
• Diarrhoea
• Runny nose
• Sneezing

Severe symptoms ( Called Anaphylaxis)

These include:

• Swelling of the tongue and/or throat
• Difficulty in swallowing or speaking
• Change in voice (hoarse voice)
• Whistling noise or persistent cough
• Difficult or noisy breathing
• Dizziness, collapse, loss of consciousness (due to a drop in blood pressure)
• Pale, floppy, sudden sleepiness in babies.

Anaphylaxis can be life-threatening and should be treated with epinephrine (adrenaline) without delay.³

Causes of peanut allergy

Peanut allergies are caused by an abnormal immune response to proteins found in peanuts. There are 11 peanut proteins responsible for allergic reactions, but Ara h 1, Ara h 2, Ara h 3 and Ara h 6 are responsible for triggering the most immunological response.⁵ Food allergies occur when the immune system produces IgE antibodies against ingested, touched, or inhaled food proteins (allergens). IgE antibodies circulate in the blood and attach to immune cells. Upon re-exposure to the allergen, it binds to these antibodies, prompting the release of large quantities of chemicals that can induce various symptoms, such as hives, itching, and redness, when released into the skin.⁶ 

Several factors contribute to the development of peanut allergies:^{7 8}

• Genetic predisposition 

Genetics play a significant role in the development of allergies, including peanut allergies. If an individual has a family history of allergies, especially peanut allergies, they may have a higher chance of developing this condition.

• Early exposure 

Research has shown that the timing of peanut exposure can influence the development of allergies. In the past, it was recommended to avoid introducing peanuts to infants early in life to prevent allergies. However, more recent guidelines suggest that introducing peanuts to infants at an appropriate age, especially those at high risk due to family history or other factors, can reduce the risk of peanut allergies. Delayed introduction may increase the likelihood of developing an allergy.

• Immune system response 

Peanut allergies are fundamentally immune system reactions gone awry. Normally, the immune system identifies and defends against harmful pathogens. However, in individuals with peanut allergies, the immune system mistakenly recognizes peanut proteins as dangerous invaders. This triggers an immune response, leading to allergy symptoms like hives, swelling, and difficulty in breathing.

• Environmental factors 

Environmental factors may also contribute to the development of peanut allergies. These factors can include exposure to pollution, changes in diet, and other lifestyle-related elements. 

• Hygiene Hypothesis

The hygiene hypothesis suggests that our modern, overly clean environments, especially in developed countries, may be contributing to the rise in allergies. Reduced exposure to certain microbes and infections during childhood may affect the development of the immune system, making it more prone to allergic reactions.

Diagnosis and testing

When you visit an allergist, the patient will undergo certain tests:^{7 9}

1. Allergen-Specific IgE Blood Test

A blood test can measure specific immunoglobulin E (IgE) antibody levels in the bloodstream in response to peanut proteins. High levels of peanut-specific IgE antibodies may indicate an allergy. 

2. Skin Prick Test (SPT)

In a skin prick test, a small amount of peanut extract is applied to the skin, and then a tiny needle is used to scratch the skin's surface. If the individual is allergic to peanuts, they may develop a localized allergic reaction at the test site, such as redness, swelling, or itching. 

3. Oral Food Challenge (OFC)

An oral food challenge is considered the gold standard for diagnosing food allergies. It involves gradually introducing small, controlled amounts of peanut protein to the individual under medical supervision. The individual is closely monitored for any allergic reactions during the challenge.

An OFC is typically conducted in a specialised allergy clinic or hospital setting.

Treatment and therapy options for peanut allergy

Four notable approaches to peanut allergy treatment include:^{10 11}

• Epinephrine

Epinephrine, commonly administered through an EpiPen, is the first line of defence in treating peanut allergies. In case of accidental exposure to peanuts leading to severe allergic reactions (anaphylaxis), epinephrine is a critical emergency intervention that can reverse symptoms such as swelling, difficulty breathing, and low blood pressure. It works by constricting blood vessels, opening airways, and stabilizing blood pressure.

• Allergen Immunotherapy

Allergen immunotherapy is an approach that involves exposing patients to small, controlled amounts of the allergen over time. This therapy can help build tolerance and reduce allergic reactions. It is usually administered as allergy shots to desensitise the patient's immune system to peanut allergens.

• Oral Immunotherapy (OIT)

OIT is a more specific form of allergen immunotherapy that involves ingesting small but increasing doses of peanut protein daily. Over time, this process helps patients build tolerance to peanuts. OIT has shown promising results in clinical trials, with many patients achieving significant protection against accidental peanut exposure.

• Sublingual Immunotherapy (SLIT)

SLIT is a less invasive form of immunotherapy that involves placing small amounts of allergen extract under the tongue, where it is absorbed into the bloodstream. While it is less studied for peanut allergies compared to OIT, SLIT has shown the potential to reduce allergic reactions to peanuts in some individuals.

In 2020, the FDA approved Palforzia as the first-ever peanut allergy treatment. Palforzia is a standardized peanut powder that is administered in a controlled manner to patients under medical supervision. Palforzia can help increase tolerance to peanuts and reduce the severity of reactions upon accidental exposure.

Cross-contamination and hidden allergens

Cross-contamination sources¹²

Hidden Allergens¹³

Summary

A peanut allergy is a severe and potentially life-threatening immune response to proteins found in peanuts. It is one of the most common food allergies, particularly in children, and its prevalence has been on the rise in recent years. When individuals with a peanut allergy come into contact with peanuts or peanut-containing products, their immune system perceives these proteins as harmful invaders and releases a surge of chemicals, including histamines, into the bloodstream. 

This immune reaction can lead to a wide range of symptoms, from mild hives and digestive issues to severe anaphylaxis, characterized by difficulty breathing, swelling of the throat, and a drop in blood pressure. Anaphylaxis is a medical emergency and requires immediate treatment with epinephrine.

Managing a peanut allergy involves strict avoidance of peanuts and peanut-derived ingredients, vigilant reading of food labels, and carrying an epinephrine auto-injector at all times. Education, awareness, and preparedness are crucial to minimize the risk of accidental exposure and ensure the safety of individuals with peanut allergies.

FAQ

How do I know if I have a peanut allergy?

To determine if you have a peanut allergy, watch for symptoms after consuming peanuts or peanut-containing foods. Common signs include hives, itching, swelling, digestive issues, and difficulty breathing. Consult an allergist for definitive testing, such as skin prick tests or blood tests, to confirm the allergy and receive proper guidance.

Can you suddenly develop a peanut allergy?

Yes, it is possible for someone to suddenly develop a peanut allergy, even if they have previously consumed peanuts, without any issues. This can occur at any age and is often due to changes in the immune system's response to peanuts. It is essential to seek medical advice if allergy symptoms arise.

Can you live a normal life with a peanut allergy?

Living a normal life with a peanut allergy is possible but requires vigilance. Individuals must strictly avoid peanuts and peanut-containing products, read labels diligently, carry an epinephrine auto-injector, and educate others about the allergy. With careful management, one can lead a fulfilling and safe life.