Peanut and tree nut allergies are types of food allergy. Food allergy occurs when the body’s immune system wrongly identifies a food as a threat. When this happens, the body releases chemicals, such as histamine, in response to exposure to the food. It is the release of these chemicals that causes the allergic symptoms
The peanut is a legume and is in the same plant family as peas, beans and lentils. Tree nuts are in different plant families and include almonds, hazelnuts, walnuts, cashew nuts, pecans, Brazil nuts, pistachios and macadamia nuts. As the plant families are different, many people only react to peanuts but not to any tree nuts, and vice versa.
Many people who are allergic to tree nuts are only allergic to one type of tree nut, but some are allergic to more. For example, it’s quite common for people with cashew nut allergy to be allergic to pistachios, and for people with walnut allergy to be allergic to pecans.
Peanut and tree nut allergies are common – they are the most commonly known foods to cause anaphylaxis. About 1 in 50 children and 1 in 200 adults in the UK have a nut allergy.
Allergic reactions to peanuts and tree nuts can happen because a person already has hay fever caused by an allergy to pollen. This is called a ‘secondary’ nut allergy and happens because of “cross-reactivity”, where the proteins in pollen are similar to the proteins in nuts. The most common tree nuts involved are hazelnuts, almonds and peanuts.
Reactions are very rarely serious and often include itching or swelling in the mouth.
The symptoms of peanut and tree nut allergy usually come on quickly, within minutes of eating the food.
Mild to moderate symptoms may include:
The term for this more serious reaction is anaphylaxis (anna-fill-axis).
Most healthcare professionals consider an allergic reaction to be anaphylaxis when it involves difficulty breathing or affects the heart rhythm or blood pressure. Any one or more of the ABC symptoms above may be present.
In extreme cases there could be a dramatic fall in blood pressure. The person may become weak and floppy and may have a sense of something terrible happening. Any of the ABC symptoms may lead to collapse and unconsciousness and, on rare occasions, can be fatal.
AIRWAY - swelling in the throat, tongue or upper airways (tightening of the throat, hoarse voice, difficulty swallowing).
BREATHING - sudden onset wheezing, breathing difficulty, noisy breathing.
CIRCULATION - dizziness, feeling faint, sudden sleepiness, tiredness, confusion, pale clammy skin, loss of consciousness.
If you think you or your child may be allergic to peanuts or tree nuts, see your GP who can refer you to a specialist allergy clinic. They can find a clinic in your area from the British Society for Allergy and Clinical Immunology (BSACI).
It’s important to get a referral even if the symptoms were mild because it can be hard to tell if future allergic reactions could be more serious.
Once you get a referral, the consultant will discuss your medical history and symptoms with you. They might suggest skin prick tests, blood tests, and food challenge tests to help diagnose the allergy and work out how serious it may be.
If you have reacted to one type of nut, the tests are likely to include a range of nuts to work out which ones are safe for you to eat.
Some clues that you or your child might be at higher risk of more serious reactions are:
If you have asthma and it is not well controlled, this could make an allergic reaction worse. Make sure you discuss this with your GP or allergy specialist and take any prescribed medicines.
If you have mild allergic symptoms, you may be prescribed antihistamine medicine that you take by mouth. If you are at higher risk of anaphylaxis, you may be prescribed adrenaline to use in an emergency.
Adrenaline comes in pre-loaded adrenaline auto-injectors (AAIs) that are designed to be easy to use.
Make sure you know how and when to use them. Ask your healthcare professional to show you how to use your specific brand of AAI. You can also find help on the manufacturer’s website and get a free trainer device to practise with.
You must carry two AAIs with you at all times, as you may need to use a second one if your symptoms don’t improve after five minutes or get worse.
The adrenaline auto-injectors prescribed in the UK are:
EpiPen®
EpiPen® is available in two doses: Adult: 0.3mgs of adrenaline Junior: 0.15 mgs of adrenaline (suitable for children weighing 5kgs – 25kgs / 1 stone 3lbs – 3 stone 13lbs)
Jext®
Jext® is available in two doses: Adult: 300 mcg of adrenaline Junior: 150 mcg of adrenaline (suitable for children weighing 15kgs – 30kgs / 4 – 4.5 stone)
Once you have been diagnosed with a peanut or tree nut allergy, you will need to avoid the nut or nuts you’re allergic to.
Read the ingredient lists on food packets carefully every time you shop. Peanuts and tree nuts are included in the list of top 14 major food allergens in the UK. This means they must be highlighted on ingredients labels, in bold for example.
Read the ingredient list every time you buy a product as manufacturers change their recipes often.
Restaurants, cafes, hotels, takeaways and other catering businesses are required by law to provide information on major allergens, including nuts and peanuts. Ask staff directly if the food you’d like to buy contains nuts or peanuts and if there is a risk of cross-contamination. Let them know that even small quantities can cause a reaction. Don’t be afraid to ask staff to check with the chef.
If you are allergic to tree nuts, avoid oils made from the nuts as well. Nut oils can be used for frying, baking and to make salad dressings.
Tree nut oils are also used in some medicines, toiletries and cosmetics. It’s difficult to know whether these could cause a reaction so it’s safest to avoid them completely. In cosmetics, they are labelled in Latin.
For more information about which foods and products can contain specific nuts and nut oils, see the list further down in this factsheet.
Research has shown that refined peanut oil will not cause allergic reactions in most people with peanut allergy. This is because it contains no or very little peanut protein, which is the part that causes allergy.
Some people with peanut allergy may be allergic to tree nuts, and some people with a tree nut allergy may be allergic to peanuts.
If you have a tree nut allergy, it’s possible to be allergic to more than one type of nut. For example, it’s quite common for people with cashew nut allergy to be allergic to pistachios, and for people with walnut allergy to be allergic to pecans.
If you have a peanut or tree nut allergy, it’s important to have allergy testing for other nuts so you know what’s safe to eat and what to avoid. It’s good to eat the nuts you are not allergic to as this helps avoid developing an allergy to those nuts in the future.
Only introduce other nuts into your diet after allergy testing and talking to your specialist to make sure they’re safe for you. You will also need to make sure there has not been cross-contamination between different nuts, such as in a packet of mixed nuts.
When eating other nuts you are not allergic to, be aware of the risk of cross-contamination. It’s possible that one type of nut will come into contact with other types during food production. Eating nuts from the shells can help reduce this risk.
Some foods have ‘nut’ in the name but are not tree nuts, such as pine nuts, coconut, nutmeg and chestnut. If you have never had a reaction to any of these foods, it’s likely that they are safe for you to eat.
Peanuts are legumes, and a small number of people with peanut allergy may react to other legumes such as lupin, soya, peas, chickpeas, fenugreek, beans and lentils.
If you’re allergic to both peanuts and tree nuts, you may be more likely to have a sesame seed allergy.
Speak to your allergy specialist to make sure you know what’s safe to eat.
Findings from the Wotnut study (21 June 2023), which assessed nut recognition in children with and without nut allergy and their parents or guardians, showed that while parents and guardians recognised nuts more reliably than children, mistakes were still common highlighting a need for improved education for dietary confidence and nut avoidance.
Images reproduced with permission of F. Heraghty, Children’s Health Ireland, from the Wotnut study DOI: 10.1111/cea.14364
People with peanut and allergy often worry that touching or smelling nuts could cause a serious reaction, but research suggests this is not common.
One small study showed that when 30 children with serious peanut allergy had contact with peanut butter through touch or smell, none of them experienced anaphylaxis and none reacted to smell. A third had a mild reaction to touch including redness, itching or rash in a small area, but these were not serious, and no medication was needed. The researchers concluded that at least nine out of ten children with similar allergies would not have a serious reaction to touch or smell, but the study only looked at peanut butter, not other forms of peanut.
In another study, 84 children were positioned half a meter away from a bowl of peanuts for half an hour and none of them had a moderate or serious reaction. The researchers also collected peanut proteins from the air and the amounts of peanut protein were so small they were very unlikely to be able to cause moderate or serious allergic reactions. These studies only looked at peanuts, but there is no reason to think that tree nuts would be any different.
Some people with nut allergies have had symptoms when travelling on aeroplanes.
As nut proteins don’t easily become airborne, the most likely sources of nut exposure during flights are:
Speak to your doctor or allergy specialist about travelling safely by plane. If you think you have reacted to breathing in nut protein in the past, then contact the airline well in advance to ask that nuts are not given out on your flight.
Between about one in five and one in ten children are thought to outgrow their nut allergies. This usually happens by the age of 4 or 5, but the age at which this happens varies so it’s helpful for your child to have regular reviews with their allergy specialist.
New treatments for peanut allergies have been studied intensively over the last decade and options are now emerging, including:
Desensitisation treatment for younger children is becoming more widespread. Read our factsheet on Immunotherapy and keep an eye on our Latest News for updates.
Provide your email address to receive our printable guide outlining emergency symptoms and actions.
Additionally, enjoy our monthly Allergy Outlook email, delivering the latest news, updates, and resources directly to your inbox.
