What is a food allergy?
A food allergy occurs when the immune system reacts to an allergen (a protein) in a food. If you have an allergy to tree nuts, your reaction is likely to occur within 20 minutes to 2 hours of eating them and can rapidly progress to life threatening. Food allergy is different to food intolerance. Food intolerance does not involve the immune system and reactions are often mild, occurring many hours after eating the food. It’s important to distinguish food intolerance from a food allergy. If you have food intolerance, you can usually eat small amounts of problem foods without a reaction as you can “tolerate” small quantities. By contrast, if you have a true food allergy, even a tiny amount of the food may trigger a serious reaction.
How common are nut allergies?
At this stage the prevalence of Australian adult tree nut allergy is unknown although studies overseas suggest between 1.1–2.0% of the population.2–5 For Australian children one study of primary school entrants from 2009 described a parent-reported food allergy prevalence of 3.8% for any nut and 3.5% for peanut.6
Although as many as one in ten Melbourne based infants at 12 months can have a food allergy,7 only one in around 1700 are likely to have anaphylaxis.8, 9 This Australian population-based HealthNuts study defined food allergy on the outcome of oral food challenge and reported a peanut allergy prevalence of 3.0% in one year olds in Melbourne.7 Tree nut data from the HealthNuts study is yet to be published. International studies indicate a children’s prevalance of tree nut allergy is between 1.8%–2.0% of the population.5, 10–12
How are tree nut allergies diagnosed?
All food allergies are diagnosed by way of testing and from clinical history. A university trained medical allergy specialist reviews results of a skin prick test and/or blood test and asks questions on what has happened on previous exposure to the suspect food/s. A diagnosis is made based on both the patients’ history and tests results. If you suspect you have a tree nut allergy, ask your doctor for a referral to an allergy specialist.
Signs and symptoms of a mild to moderate allergic reaction to any food
In people with food allergies, common reactions include:
- Swelling of the lips, face, eyes
- Hives or welts
- Tingling in the mouth
- Abdominal pain, vomiting
Signs and symptoms of a severe allergic reaction or anaphylaxis
- Difficult/noisy breathing
- Swelling of the tongue
- Swelling/tightness in the throat
- Difficulty talking/ hoarse voice
- Persistent dizziness or collapse
- Young children can become pale and limp
Any allergic reaction has the potential to become life threatening however most allergies are mild or moderate. Someone who has previously had anaphylaxis is at greater risk of another episode. Whilst the prevalence of food allergy and anaphylaxis has increased this decade, death from anaphylaxis remain rare. Teenagers and young adults with peanut and tree nut allergy are at greatest risk of fatal allergic reactions. Those at high risk of anaphylaxis who have been prescribed an adrenaline autoinjector should keep their adrenaline close by (and easily accessible) at all times.
Emergency medication comes in the form of an adrenaline autoinjector called either an EpiPen® or Anapen®. An Action Plan for Anaphylaxis must be kept with the autoinjector and followed if signs of an allergic reaction occur. Those at risk of anaphylaxis and their carers need always be prepared for accidental ingestion. Parents can teach their allergic children, at an age appropriate time, to manage their condition by encouraging them to ask questions, read labels, identify nuts,13 and carry and administer medications. Children and teens with allergies need to feel comfortable and secure in their ability to make their own decisions about food. Peer support is also an important part of this process.
What is the best treatment for tree nut allergy?
If you have a known allergy to one type of nut, it is often recommended that you avoid all nuts until carefully controlled and administered medical food challenge tests can determine if you are allergic to other nuts. You will require a definite diagnosis and a planned approach that avoids the allergic food. Consultation with a Clinical Immunologist and Allergist is recommended. It may mean that you will need to avoid certain nuts but may be able to eat others from their shell. Reading ingredient labels for all foods, cosmetics, lotions, medication (both over the counter and prescribed) and herbal treatments is also key. If unsure about the ingredients in a product, do not eat or use it until you have contacted the manufacturer. Consultation with an Accredited Practising Dietitian (APD) who specialises in food allergy may also help.
How do I know if a product contains nuts?
In 2002 it became law to state the presence of commonly allergenic foods (including nuts) on packaged food labels.
Always read ingredient lists carefully. If you have a nut allergy, avoid products that contain the nuts you are allergic to. Some common nut ingredient terms are listed here. This list has been developed as a guide only. Other ingredients may contain, or have come into contact with, nuts. Always check with the manufacturer if you are unsure.
In addition to this labelling, many food manufacturers choose to highlight the risk of accidental cross-contact between products that do contain allergens and products that do not contain allergens, sometimes using statements such as “May contain traces of peanuts or tree nuts”.
If you have been cleared to eat certain types of nuts it may be best to buy those nuts in shell to avoid any cross-contact between nut varieties. Remember too if eating away from home, always ask about food content; do not presume food ‘should’ be fine because you have had that dish before or have eaten at that venue before.
How to get all the nutrition that nuts contain so you’re not missing out?
If you do have nut allergies a balanced diet will give you the nutrients you need to maintain your health and wellbeing. By excluding nuts and products that contain nuts you may need to pay extra attention to the foods that make up your daily diet. If you believe you may be missing essential nutrients as a result of dietary restrictions you can consult your doctor or your local Accredited Practicing Dietitian who has experience in food allergy.
Check these products/dishes for the presence of nuts:
- Maloney JM, et al. The use of serum-specific IgE measurements for the diagnosis of peanut, tree nut, and seed allergy. The Journal of allergy and clinical immunology. 2008 Jul;122(1):145-51
- Zuidmeer L, et al. The prevalence of plant food allergies: A systematic review. Journal of Allergy and Clinical Immunology. 2008 May;121(5):1210-8.
- Ben-Shoshan M, et al. A population-based study on peanut, tree nut, fish, shellfish, and sesame allergy prevalence in Canada. The Journal of allergy and clinical immunology. 2010 Jun;125(6):1327-35.
- Sicherer SH, et al. US prevalence of self-reported peanut, tree nut, and sesame allergy: 11-year follow-up. Journal of Allergy and Clinical Immunology. 2010 Jun;125(6):1322-6.
- McWilliam V, et al. The Prevalence of Tree Nut Allergy: A Systematic Review. Curr Allergy Asthma Rep. 2015;15(9):54.
- Kljakovic M, et al. The parent-reported prevalence and management of peanut and nut allergy in school children in the Australian Capital Territory. Journal of paediatrics and child health. 2009 Mar;45(3):98-103.
- Osborne NJ, et al. Prevalence of challenge-proven IgE-mediated food allergy using population-based sampling and predetermined challenge criteria in infants. The Journal of allergy and clinical immunology. 2011 Mar; 127(3):668-76 e1-2.
- Tang MLK, Osborne N, Allen K. Epidemiology of anaphylaxis. Current opinion in allergy and clinical immunology. 2009 Aug;9(4):351-6.
- Clark S, Camargo CA, Jr. Epidemiology of anaphylaxis. Immunology and allergy clinics of North America. 2007 May;27(2):145-63, v.
- Ahn K, et al. Prevalence of immediate-type food allergy in Korean schoolchildren: A population-based study. Allergy and Asthma Proceedings. 2012 Nov-Dec;33(6):481-7.
- Shek LPC, et al. A population-based questionnaire survey on the prevalence of peanut, tree nut, and shellfish allergy in 2 Asian populations. Journal of Allergy and Clinical Immunology. 2010 Aug;126(2):324-U50.
- Venter C, et al. Prevalence of sensitization reported and objectively assessed food hypersensitivity amongst six-year-old children: a population-based study. Pediatric allergy and immunology: official publication of the European Society of Pediatric Allergy and Immunology. 2006 Aug;17(5):356-63.
- Hostetler TL, Hostetler SG, Phillips G, Martin BL. The ability of adults and children to visually identify peanuts and tree nuts. Ann Allergy Asthma Immunol. 2012 Jan;108(1):25-9.