Understanding peanut allergy - An expert guide to staying safe

Peanut allergy is a serious medical condition, on the increase over recent decades, and usually develops in early childhood.¹ Peanut is also the most common cause of severe food allergy reactions.² So it’s important to know how to avoid peanuts and what to do in the event of accidental contact.

Peanut allergy affects around 2% of people in Western countries, according to The Global Burden of Illness of Peanut Allergy: A Comprehensive Literature Review, published in 2021.³ Around 20% of children with a peanut allergy may outgrow it.¹ But for many it is a lifelong condition that needs careful management.²

This guide will walk you through understanding peanut allergy, recognising the signs of a food allergy reaction and avoiding foods that might trigger it. Learn about allergy testing and treatment, and get tips for living a full life with a peanut allergy.

What is a peanut allergy?

A peanut allergy is an overreaction of the body’s immune system to one or more peanut proteins. That means when a person with a peanut allergy comes into contact with peanut proteins, their immune system mistakenly identifies them as a harmful intruder and releases chemicals, causing an allergic reaction.⁴

It’s a Type 1 allergic reaction.² Allergies like this develop in two stages. First contact with peanut puts your immune system on alert and it produces Immunoglobulin E (IgE) antibodies. Now you’re sensitised, which may be all that happens. Not everyone goes on to develop an allergy.

But you could do the next time you eat peanut. The IgE antibodies recognise the allergen and mobilise cells around your body to release histamine and other chemicals.⁴ This is what causes your peanut allergy symptoms.

Peanut allergy is often grouped together with nut allergies but different proteins are involved.^5,6

Is peanut allergy the same as nut allergy?

Peanuts are legumes, like peas and lentils, and grow under the ground (which is why they’re also called groundnuts).⁵ They aren’t related to almonds, walnuts and other tree nuts but their proteins are quite similar.⁶ Between 25 and 40% of people with peanut allergy also have a tree nut allergy, according to the British Society for Allergy and Clinical Immunology (BSACI).⁷

What does an allergic reaction to peanuts look like?

Peanut allergy symptoms typically appear soon after eating peanuts, although it can take up to 4 hours.^2,5 You may feel uncomfortable or quite unwell. Some common symptoms are an itchy red rash (hives), tingling or itching in the mouth, and swelling of the face, mouth or throat.⁵ 

You might get some or all of these symptoms too:^1,5

• Difficulty swallowing
• Wheezing or shortness of breath
• Feeling dizzy and lightheaded
• Feeling sick (nausea) or vomiting
• Stomach pain or diarrhoea

The signs of an allergic reaction to peanuts can range from mild to severe.¹ How long they last can also vary.² Sometimes the symptoms listed above can be the first signs of a severe reaction (anaphylaxis), which can be life-threatening.⁸

Severe allergic reactions: Anaphylaxis

A peanut allergy can cause anaphylaxis, a life-threatening allergic reaction that affects the whole body and needs immediate treatment.¹ If you spot the symptoms, use an adrenaline device (if you have access to one). Then call 999 and say you suspect anaphylaxis.⁹

Symptoms of anaphylaxis include: ^5,9,10

• Airways: Swelling of the tongue or throat; throat and chest tightness
• Breathing: Wheezing, coughing or noisy breathing. Difficulty breathing or breathing very fast
• Circulation: A drop in blood pressure, feeling dizzy or faint, or collapsing
• Gastrointestinal symptoms: Nausea and vomiting, diarrhoea, abdominal pain
• Skin symptoms: Skin that looks blue, grey or paler than usual, a widespread itchy skin rash
• Sense of impending doom

Children may become irritable, stop playing and cling to mum or dad.⁹ 

How long does a peanut allergy reaction last?

A mild reaction, like hives or an itchy mouth, may last less than an hour. A severe reaction can last much longer.² Always go to hospital if you have a severe allergic reaction as there can be a second wave of symptoms up to 8 hours later.² 

Foods to avoid that might trigger a peanut allergy

It’s important to completely avoid peanuts and all peanut-containing foods. There are obvious sources like peanut butter but peanut proteins can be hidden in many processed foods too. Always check food labels carefully for any peanut ingredients and watch out for cross-contamination too.

Foods that contain peanuts

Manufacturers must list peanuts and other major allergens on food packaging. The word should be emphasised (in bold type, for example) in the ingredients so you can see it easily.¹ It’s often more difficult to know what’s in non-packaged foods so ask or avoid that food if you’re not sure. 

Here are some hidden sources of peanuts to watch out for:^5,11,12

• Baked goods: Like biscuits, pastries and cakes
• Breakfast cereals: As well as cereal bars
• Foods cooked in groundnut oil: Groundnut (peanut) oil is used in cooking. A study by J Hourihane and colleagues, published in the British Medical Journal in 1997, showed that refined peanut oil does not cause symptoms for people with peanut allergy, but unrefined oil may do. If you’re not sure whether it’s refined, it would be safest to avoid it.
• Protein and energy bars¹²
• Savoury snacks: Including Bombay mix and fruit and nut mix
• Sweet treats: Chocolate,⁵ some chocolate spreads, frozen desserts and ice-cream
• Vegan and vegetarian foods: Like nut roasts, some veggie sausages and burgers
• World foods: Including satay sauce and curries, some African and Asian dishes

Cross-contamination risks

You might come across foods with precautionary allergen labelling. This is voluntary and the wording can vary; for example ‘may contain nuts’ or ‘made in a factory that processes peanuts’. Speak to your doctor about whether you should avoid foods with statements like this.⁵ 

Cross-contamination can also happen in places like ice cream parlours, restaurant kitchens and at home – yours or someone else’s. That might be from crockery, cutlery or cooking equipment.¹ Washing up and wiping up carefully can help. 

If you're also allergic to one or more tree nuts, you’ll need to avoid those too. And bear in mind that foods made from tree nuts might also be contaminated with peanuts.⁵

Peanuts in medicines and toiletries

Peanut oil is used in some vitamins, ear drops, creams for nappy rash and eyeliner pencils, as well as in some types of injections. With toiletries and cosmetics, the convention is to use Latin names for plant-based ingredients. Arachis or Arachis hypogaea means peanut.¹³

You could try asking the manufacturer if the peanut oil they use is refined, which makes it unlikely to cause an allergic reaction.¹¹ Or get advice from your doctor or allergy specialist. 

Medicines that contain soya sometimes have warnings that people with peanut allergy should avoid them. This is because some people are allergic to both ingredients.¹³

How to test for peanut allergy

Your doctor may suggest allergy testing to help confirm suspected peanut allergies. The most common types are skin prick tests, and blood tests but the doctor might suggest an oral food challenge if there is any doubt about the diagnosis.² 

When you go to your first allergy appointment, be ready to describe any symptoms you or your child have had and when they happened.

Skin prick tests

During a skin prick test, clinic staff will put drops of peanut extract and possibly other allergens on your arm and gently prick the skin. A raised, itchy bump after around 15 minutes is a positive result and means you could be allergic, especially if you’ve had reactions to peanuts.² Your doctor will interpret the results for you.

Blood tests

You may have a blood test instead of or as well as a skin prick test. It measures specific IgE antibodies to one or more allergenic proteins.² Clinic staff take a small amount of blood and send it away to a lab for testing so you’ll have to wait to get the results. 

Another type of blood test can identify exactly which peanut proteins you’re allergic to. This can be useful for helping to show if you’re at greater risk of a severe reaction.¹⁴

What happens in an oral food challenge?

Oral food challenges are the gold standard for diagnosing food allergy. They’re often used when other test results aren’t clear or to see if a child has outgrown their peanut allergy. A challenge involves eating tiny, controlled amounts of peanut while medical staff monitor you for a reaction.² 

You’ll probably need to stop taking your antihistamine before the test as it can minimise early warning signs of a reaction.¹⁵ 

Living with peanut allergy

Living with a peanut allergy requires vigilance and avoiding peanuts completely. That means reading food labels, and asking detailed questions in places like restaurants and friends’ homes.² It might feel awkward at first but it’s important to get used to telling people about your peanut allergy.

Here are six tips for living with peanut allergy. 

1. Be prepared for an emergency: It’s also a good idea to have an allergy management plan that includes what to do in an emergency.² Talk to your doctor about what this should include and share it with family, friends and school or work.

2. Carry emergency medication: Ideally have two devices for administering adrenaline with you at all times because of the risk of anaphylaxis. Make sure the devices are in date and stored correctly. Show your friends and family how it works too.¹⁰

3. Wear medical alert jewellery: If you’re at risk of anaphylaxis, then a medical alert bracelet or necklace can share critical information about your allergies when you can’t – especially helpful when travelling.¹⁰

4. Read food labels: Carefully check food labels on all packaged foods. That even includes pet  food and bird food, which can contain peanuts. Allergens from pet food can linger in the animal’s saliva and transfer to whomever they lick.¹⁶

5. Kiss carefully: Traces of nut can also stay in human saliva – for several hours. Even brushing teeth or rinsing the mouth may not remove them.¹⁷ So take care when kissing (or sharing cutlery, cups and glasses).

6. Empower your child to stay safe: Involve your child in managing their own allergy and when you talk about it with others. That will help them to be independent one day. Teach them how to read food labels and not to share food at school or parties. Encourage them to wash their hands before and after eating.² 

Peanut allergy treatment options

The right option depends on the severity of your peanut allergy symptoms. For an anaphylactic reaction, the emergency treatment is adrenaline, given immediately.⁹ Milder peanut allergy symptoms may respond to antihistamine.⁵  Your doctor will explain these options in case you come into accidental contact with peanut.

Treatment to increase the body’s tolerance of peanut may also be an option for some people. You would still need to avoid peanut.¹⁸

Treatment for severe reactions

Adrenaline is the only effective treatment for anaphylaxis and it can be lifesaving. The drug works all across the body: by relieving and preventing the airway swelling that causes breathing difficulties; and also by tackling dangerously low blood pressure. If the first dose doesn’t work after 5-15 minutes, be ready to administer a second dose.⁹

Make sure family and friends know how to use your adrenaline device too.¹⁰ An allergy action plan can help everyone remember what to do in the event of anaphylaxis.²

Treatment to lower the risk of peanut anaphylaxis

Peanut allergy treatment called oral immunotherapy is available for children aged 4-17 years old. It involves eating carefully controlled doses of peanut under medical supervision. The goal is to increase the amount of peanut protein the child’s immune system can tolerate and so reduce the risk of a severe reaction.¹⁸

After allergy immunotherapy treatment ends, kids then take their maintenance dose in real peanuts, which means about one and a half a day. They also need to keep avoiding peanut otherwise and carry emergency medication.

Doctors need to assess children before embarking on a course of peanut immunotherapy. Severe or uncontrolled asthma in the last 12 months would rule it out.

The short version

Peanut allergy is a condition where the immune system overreacts to peanut proteins. It’s becoming more common and can be serious.  Symptoms of a peanut reaction can range from mild, like hives and an itchy mouth, to life-threatening anaphylaxis.¹ 

The main way to stay safe is to avoid peanuts. This means carefully checking food labels and asking about ingredients when eating out. For people at risk of anaphylaxis, it’s ideal to carry two adrenaline self-administered devices at all times.¹⁰ You’ll need to plan ahead and have an action plan that’s shared with other people you spend time with.² The right information and support will help you to manage the condition and live a full life.