What Causes a Peanut Allergy?

Medically reviewed by Daniel More, MDMedically reviewed by Daniel More, MD

A peanut allergy is a potentially life-threatening allergic reaction caused by your immune system in response to peanuts. An allergic reaction occurs when your immune system mistakenly identifies peanut protein as harmful.

Peanut allergies affect approximately 6.1 million Americans. This allergy is the third most common food allergy. About 20% of people outgrow peanut allergies as they age.

Signs you may be allergic to peanuts include mild symptoms like itching or more serious reactions like dizziness or fainting when exposed to peanuts. Depending on the severity of your allergy, you can experience symptoms from eating peanuts, breathing in peanut dust, or having them make contact with your skin.

Symptoms

Peanut allergies can occur in people as early as four months old. They typically begin before age two. Symptoms can range from mild to severe. Symptoms may occur within minutes to hours after exposure to peanuts.

You may not experience the same symptoms with each exposure, and symptoms can become more severe over time. Symptoms that progress in severity may also affect the nervous system.

Mild Symptoms

Common early and mild symptoms of a peanut allergy include:

• Stomach upset or cramps

• Itchy skin or mouth

• Hives (red, raised, itchy welts)

• Redness

• Swelling

• Worsening of eczema (a chronic inflammatory skin condition that commonly co-occurs with allergies)

Moderate Symptoms

Moderate symptoms typically affect your skin and gastrointestinal (stomach and intestinal) health. Moderate symptoms that continue to worsen for weeks require medical attention.

The following moderate symptoms can occur within minutes or progress from mild symptoms:

• Coughing

• More intense nausea

• Vomiting

• Diarrhea

• More hives or swelling

• Mild tightness in the chest or wheezing

• Severe skin rash

• Swelling of the lips and tongue

• Tingling in the mouth and throat

Life-Threatening Symptoms

Anaphylaxis is a severe and potentially life-threatening allergic reaction that can occur as a result of a peanut allergy. Getting immediate treatment for moderate symptoms when you notice them can prevent your allergic reaction from progressing to anaphylaxis.

Anaphylactic shock can also lead to cardiac arrest (your heart stops pumping blood to the rest of your body). Severe anaphylaxis may also require overnight medical care.

Symptoms of anaphylaxis include:

• Difficulty breathing or shortness of breath

• A drop in blood pressure causing dizziness or fainting

• Swelling of the tongue or throat that obstructs breathing

• Hoarseness in your voice

• Dizziness

• Lightheadedness

• Severe nausea or vomiting

• Stridor (high-pitched breathing noise from the upper airway)

• Rapid pulse or weak pulse

• Loss of consciousness

Causes

Your immune system protects you by making it more difficult for harmful substances to attack your body. Peanut allergies occur when your immune system mistakenly identifies peanut proteins as dangerous. The immune system triggers symptoms like tingling in the mouth and throat.

If you have a peanut allergy, your immune system produces immunoglobulin E (IgE) when it comes into contact with peanuts. IgE are antibodies that trigger the release of chemicals like histamine, which signal your immune system to react.

Risk Factors

Researchers do not know why some people develop peanut allergies while others do not. Genetics may play a role in whether you develop a peanut allergy. An allergy to peanuts can be inherited from a parent.

Some research has made connections between atopic conditions (eczema, asthma, allergic rhinitis, etc.) and the likelihood of developing peanut allergies. Atopic conditions are caused by genetic predispositions to certain allergens.

A microbiome (good and bacteria) imbalance can also increase your risk of developing a peanut allergy. If you are allergic to other foods, you may also want to get tested for a peanut allergy.

How Are Peanut Allergies Diagnosed?

Your healthcare provider will determine if you have an allergy by carefully reviewing your medical history, symptoms, and the severity of your allergic reactions. Before conducting any tests, they will ask if your parents or a sibling has a peanut allergy.

They may use the following diagnostic tests to rule out other potential causes of your symptoms:

• Skin prick test: The provider drops some peanut extract onto your skin with a needle or plastic device. If you're allergic, a raised, itchy bump will appear on your skin where the extract was dropped within 15-20 minutes.

• Blood test: A blood test can check for specific antibodies like immunoglobulin E (IgE), which is involved in allergic reactions.

• Oral food challenge (OFC): An OFC involves eating increasing amounts of peanut protein under medical supervision.

Treatment

Treatment for a peanut allergy consists of alleviating any symptoms of an allergic reaction and avoiding peanut products. It is important to carefully read food labels and be mindful of when foods may be cooked with peanut oil or other peanut-based products.

Your provider might prescribe the following medications for mild to moderate symptoms:

• Antihistamines: Relieve mild allergy symptoms by blocking histamine, which causes itching and hives

• Corticosteroids: Reduce inflammation, itching, and hives by suppressing your immune system's response

• Bronchodilators: Relax airway muscles to help you breathe better and relieve wheezing or chest tightness

• Xolair (omalizumab): An injection that lessens the severity of symptoms after exposure

The U.S. Food and Drug Administration (FDA) has also approved some versions of immunotherapy to reduce symptoms in children with peanut allergies.

Your healthcare provider may also suggest carrying an EpiPen (epinephrine) for cases of accidental peanut exposure. An EpiPen is a medication you inject into your thigh to help subdue an allergic reaction while you wait for emergency assistance.

Prevention

Newer research suggests that introducing peanuts at around four to six months may reduce allergy risks, especially for high-risk infants. Researchers found that babies exposed to peanuts and peanut snacks earlier had a higher tolerance for peanuts.

Some studies suggest that eating allergenic foods while breastfeeding may prevent allergies. However, more research is needed to know how effective this is.

Related Conditions

Peanut allergies often co-occur with other health conditions that also influence your immune system.

Children who develop peanut allergies are also 27% more likely to develop a tree nut allergy by age 6. Tree nuts include almonds, cashews, peanuts, and more.

Some of the most common food allergies include cow's milk, eggs, and peanuts. About 40% of children with food allergies are allergic to more than one food. Having food allergies also makes it more likely that you may develop atopic health conditions like eczema, asthma, and allergic rhinitis (seasonal allergies).

Living With Peanut Allergies

Having a peanut allergy can be challenging to navigate at times. When you go to restaurants, consider notifying the restaurant of your allergy to avoid having an unexpected allergic reaction. Regularly check food labels to ensure they don't contain peanuts.

Carry an EpiPen and teach your peers and loved ones how to use it. This can give you peace of mind in case of accidental exposure. If you suspect a peanut allergy or sensitivity, consult your healthcare provider for an allergy test.

Frequently Asked Questions

Can peanut allergies go away?

Milk, egg, wheat, and soy allergies often resolve throughout childhood. However, allergies to fish, peanuts, shellfish, and tree nuts are typically lifelong. About 20% of children outgrow their peanut allergy, but peanut allergy symptoms can also worsen with age.

Can you be only slightly allergic to peanuts?

The severity of peanut allergies can be unpredictable. Someone who has mild allergy symptoms in the past might have more severe, life-threatening reactions later in life. Anyone with a peanut allergy should avoid all peanut products and carry an epinephrine auto-injector for emergency use.

What is the difference between a peanut allergy and peanut sensitivity?

A peanut allergy involves an overreaction by your immune system, potentially causing severe or life-threatening symptoms. Food sensitivity or intolerance arises when your body can not break down certain foods, but are not life-threatening.

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