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Nut allergy

Published by Bupa's health information team, July 2008.

This factsheet is for people who have a nut allergy, or who would like information about it.

If you have an allergy, it means that your body's immune system reacts to an allergen - a substance that causes an allergic reaction. An allergic reaction happens when your body's immune system mistakes the allergen, for example nuts, for a harmful invader. Allergens aren't usually harmful and most people aren't sensitive to them.

About nut allergy

Nuts are one of the most common causes of food allergies. If you have a nut allergy, it's most likely that you react to peanuts or tree nuts. Tree nuts include Brazils, almonds, cashews, hazelnuts, walnuts and pecans. Peanuts, also known as groundnuts or monkey nuts, aren't actually nuts but legumes - related to peas and beans - and grow underground.

You can develop an allergy to nuts (or any other food) at any age. However, it's most likely to happen before the age of three. The number of people in the UK who may be allergic to nuts is increasing. Research from 2002 shows that one in 70 children is allergic to peanuts, compared to one in 200 ten years before. More recently, a report was published suggesting a quarter of a million children (one in 50) in the UK are allergic to nuts.

If you are allergic to one type of tree nut, it's likely that you will react to others. You may also have a peanut allergy. If you have a peanut allergy, it's possible that you will be allergic to other legumes such as soya beans and green beans, and also to tree nuts.

Symptoms of nut allergy

The symptoms of a nut allergy are likely to be different for everyone with the condition and they will vary in severity. Your symptoms will usually occur within a few minutes of eating nuts. Some of the most common, milder symptoms of nut allergy include:

  • itchy eyes or skin
  • rash
  • runny nose or sneezing
  • breathlessness
  • tingling of lips, tongue or mouth
  • digestive problems such as stomach cramps, diarrhoea and vomiting

If your nut allergy is more serious, you may also have:

  • swelling of the lips, tongue, throat or face - if your throat swells, you may find it difficult to breathe
  • dizziness

With a very severe nut allergy, you or your child may develop anaphylaxis. This is when the airways from the lungs become swollen and make breathing difficult. There is also likely to be a drop in blood pressure and an increase in heart rate. You or your child may collapse or become unconscious.

If you or your child is severely allergic to nuts or peanuts, your allergy may be triggered just by touching or being near someone who is eating them or has done recently. You may also have a reaction as a result of being in the same room where nuts have been. Using cutlery or crockery that has been contaminated with traces of nuts may also cause an allergic reaction.

Causes of nut allergy

If you have a nut allergy, when you come into contact with nuts, IgE antibodies are produced. Antibodies are usually only released to fight infection, but in this instance your body believes the nut is harmful. This leads to certain cells in your body called mast cells releasing chemicals. One of these is histamine which triggers the symptoms of an allergic reaction such as a rash or swelling.

The exact reasons why some people are allergic to nuts aren't fully understood at present. There is some evidence that children who are given nuts early on in their diet may become sensitised. This may also happen before the baby is born while he/she is still in the womb. It's possible that a child may develop a nut allergy after birth if his/her mother eats nuts while she is breastfeeding. However, new evidence suggests that this may not be the case and it may be necessary to expose babies to possible food allergens so they don't become sensitised to them.

If you or your child have other allergies or conditions such as eczema or asthma, a nut allergy may be more likely to develop. If someone else in your family has these conditions, this can also increase your risk of having an allergy, although it may not be to the same thing.

There is some evidence that some babies may become sensitised to nuts as a result of being treated with skin treatments for eczema or other allergic conditions that contain peanut oil, or from peanut oil found in certain sorts of formula milk and nipple creams.

An allergic reaction may be caused by:

  • direct contact through eating or skin contact
  • cross contact as a result of a product being contaminated with nuts
  • breathing in the allergen, for example from dust or sprays that contain nuts or nut oils

Diagnosis of nut allergy

If you think you or your child is allergic to nuts, you should see your GP. He or she will ask about the symptoms and examine you or your child. Your GP may also ask about your medical history.

It's possible that you have a nut intolerance. This is different from a nut allergy as it doesn't affect the immune system. Instead it involves the digestive system and may cause symptoms such as bloating, indigestion and migraines.

Blood tests

One method of testing for food allergies is the RAST (radioallergosorbent test). This measures the level of IgE antibodies for a specific allergen in your blood. RASTs may produce false positive results - this means the test may show you are allergic to something when actually you aren't - or false negative results suggesting you aren't allergic to something when really you are. However, it has the advantage that it can be used to confirm a diagnosis if you have a severe food allergy. This is because a sample of your blood is tested, so there is no risk of the food causing anaphylaxis.

Skin prick tests

It's also possible that you will be offered skin prick tests to help determine exactly what you are allergic to. This involves introducing tiny amounts of different allergens to your skin and seeing which ones cause an allergic reaction. The test will be done in hospital or at your GP's surgery and only a very small amount of the allergen is used. The test is safe for most people unless you or your child has had an obvious anaphylactic reaction to an allergen in the past.

Treatment of nut allergy

The main treatment for nut allergies is to try not to eat nuts or products that may contain them.

Your GP may prescribe you antihistamine treatments in case you have a mild reaction. You can also buy some antihistamines without a prescription. Always ask your GP for advice and read the patient information leaflet that comes with your medicine.

If you or your child has a very severe nut allergy and there is a risk of an allergic reaction causing anaphylaxis, you will need to carry adrenaline with you at all times. This is a hormone (chemical that occurs naturally in your body) that relaxes muscles and so helps to reduce any swelling and make breathing easier. Single doses of adrenaline are available in the form of an EpiPen or AnaPen. This consists of a sterile syringe of adrenaline that is ready to be used in an emergency. Your GP will prescribe this for you if you are at risk of anaphylaxis. You will need to go to hospital immediately if you have anaphylaxis, even if using an EpiPen or AnaPen has helped to reduce the reaction.

If you are at risk of a serious reaction, it's important to wear a medical identification bracelet, tag or similar. This gives details of your allergy and a telephone number that anyone can call for more information in case you have a serious allergic reaction.

Living with nut allergy

If you or your child has a nut allergy, it's important to check the packaging of food carefully to find out if it contains nut. In 2005, new rules were introduced which mean that all pre-packed food sold in the UK and the European Union must say on the label whether it contains nuts.

Even if a food doesn't contain any nuts, it may have been contaminated with traces of nut during production. If this is a possibility, the label will usually state that the product 'may contain nut traces'. It's important to be aware that this isn't a legal requirement so there may be some foods that have come into contact with nuts but aren't labelled.

The allergens in nuts and peanuts aren't destroyed by heating, for example if they are roasted. In fact, studies have shown that this may actually make peanuts more likely to cause a reaction.

Nut and peanut allergies affect everyone differently. Nut allergy was once considered to be a life-long condition. However, it's now thought that between one in four and one in five children with peanut allergy grow out of it.

If you or your child have even only minor symptoms after eating nuts, it's important not to carry on eating them as this could lead to you becoming more sensitive and having a more severe reaction in the future. See your GP if you think you or your child may have symptoms of a nut allergy.

Further information

Related topics

Sources

This information was published by Bupa's health information team and is based on reputable sources of medical evidence. It has been peer reviewed by Dr WH Simpson, General Practitioner, and by Bupa doctors. It has also been reviewed by The Anaphylaxis Campaign. The content is intended for general information only and does not replace the need for personal advice from a qualified health professional.

Publication date: July 2008.

 

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