Itching to know: All about food allergies and intolerances
Food allergies and intolerances are a huge health issue but what exactly are they and why do so many people seem to have them? We answer the commonly asked questions and sortthe facts from the sensational.
Tell someone who has almost died after eating a single peanut that you're 'allergic' to garlic because it makes you burp and don't expect any sympathy. Calling any reaction to eating a certain food an 'allergy' is a common misconception. And part of the problem is the word 'allergy' itself. It originated 100 years ago in medical circles to describe any reactions to food, pollen and insect stings. By 1925 the definition was narrowed to reactions that involved the immune system, and that's how it stands today. If the reaction isn't coming from your immune system, the experts call it an intolerance.
The allergy-immune system connection
A food allergy is an over-reaction by the body's immune system to foods that would not ordinarily pose a real threat. It's a bit like calling in the SWAT team for a simple knock at the door - eating a peanut triggers a flood of chemicals that produce immediate, and sometimes even life-threatening symptoms.
'Anaphylaxis' is the most dangerous form of allergic reaction - a person's blood pressure drops and their airways - the tubes that carry the air from their nose and mouth to their lungs - can close. It kills 10 to 20 Australians each year and about one-third of cases are caused by foods. People with asthma and those who have had previous lesser reactions are at risk of having a severe allergic reaction, as are those who've had a large skin-prick test result (see below).
Because the immune system is involved, your body has to know the food before it can recognise it as a hostile threat. That explains why a toddler might eat a peanut butter sandwich for the first time and be fine but the next time they react.
The reactions we're talking about are caused by chemicals such as histamine, which are produced by the body and released from the mast cells just under the surface of our skin, in the gut lining and in the nose and throat. These natural chemicals cause skin welts and rashes, make the gut reject its contents, and cause noses to run and airways to swell.
Pollen-allergic people can also react to raw food with itching, blistering and swelling of the lips, mouth and throat. The most severe reactions occur to celery, kiwifruit, peaches, apricots, apples and hazelnuts. The cooked version is usually okay.
Though rare, a combination of food and exercise can cause hives or even anaphylaxis. This phenomenon can happen with wheat and other cereals, celery, seafood, nuts, fruit and some vegetables.
Latex-allergic people often have other allergies to grass pollens and dust mites, and about half get an itchy mouth or swelling in the throat with foods including banana, avocado, kiwifruit, strawberries and chestnuts.
Allergy to snails has been reported and can trigger a severe asthma attack. But fortunately this has never been seen in Australia.
Kids and allergies
The major concern with true allergies is this connection with the immune system because they can get worse each time you're exposed to the food (or allergen). So if you suspect an allergy, especially in your children as you give them new foods for the first time, visit your family doctor as soon as possible. They will refer you to an allergy specialist or clinic for testing (see 'Tackling allergies' section below for a description of the tests).
The tendency to have allergies (atopy) is strongly hereditary - 'atopic' parents are likely to have children with allergies. For most people allergies aren't dangerous but can be extremely annoying and even debilitating (think of bad hay fever, for example).
Food allergy is mainly a problem for infants, toddlers and young children. In fact, 6-8% of babies will have an allergy, often to two or three foods and usually associated with atopic eczema. Fortunately, most food allergies resolve before school age, but nut and seafood allergies tend to persist, affecting about 1% of adults.
Today it's not uncommon for a school to have an EpiPen (an automatic injector containing adrenaline) on hand to deal with life-threatening allergic reactions. The Australasian Society of Clinical Immunology and Allergy (ASCIA) has guidelines for minimising the risk of food-induced anaphylaxis in schools, preschools and childcare centres that include 'free zones' for nuts and eggs or whatever is necessary to protect allergic children. Some schools have adopted nut-free canteens and ask parents to refrain from sending peanut butter sandwiches and other nut products with their kids into school. Nutella, muesli bars and nut mixes all need to stay at home.
Besides peanuts, other nuts - including almonds, Brazil nuts, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts - can cause severe reactions in sensitive children.
A growing problem
There has been a 12-fold rise in food allergies in Australian children since 1995 and there is much speculation as to why this is happening. The hygiene hypothesis proposes that today's clean environments leave our immune systems with too little to do, encouraging it to look at the wrong culprits. But why are nuts such a problem? Increased peanut consumption has been blamed, with peanuts being promoted as a health food and used as a common ingredient in Asian and vegetarian dishes. It's also said roasting makes nuts more allergenic.
What is food intolerance?
Food intolerance, by contrast to food allergy, is a more subtle reaction - there's never any threat of a sudden death. If you are intolerant to gluten, for example, you're likely to feel uncomfortable, chronic symptoms such as abdominal pain and bloating when you eat it. Food intolerance is a far more common problem than food allergy and likely to be on the rise, possibly due to changes in our diet and an over-use of food additives.
We don't know as yet exactly how food intolerance works, but immunologist Robert Loblay suspects it is triggered when nerve endings in different parts of the body are stimulated. "Just like medications can have side effects in some people, so can food," he explains.
Food intolerance can be hard to pinpoint because the symptoms can be vague, multiple, intermittent and varying in severity. You can be born with an intolerance or it may develop at any stage in your life. You can be intolerant to a certain food, such as milk or wheat, or a natural or artificial flavour, colour or preservative in a food product. Often the culprits are foods that are eaten regularly - there can even be a craving for that food because it makes you feel good when you first eat it. And like allergies, intolerances also tend to run in families.
To help identify and manage a food intolerance, it's best to see a dietitian who will put you on an elimination diet and monitor the results. It can take many months and lots of patience but identifying the problem food and knowing where to find it and how to avoid it could change your life.
Unlike an allergy, a food intolerance is not an all-or-nothing condition. With intolerance, a small amount of the food may not cause any symptoms but a larger amount can, and you may react to a gradual build-up over a few days. One or two strawberries or a slice of fresh tomato may be tolerated with no symptoms at all whereas eating a larger amount, say, a whole punnet or a tomato sauce, can be too much. Every person with a food intolerance will have a different story.
Friendly Food (Murdoch Books, rrp $29.95), with its easy-to-use food chemical listings and recipes, is a good resource for people with intolerances.
Allergy versus intolerance
Involves the immune system
Does not involve the immune system
Skin-prick testing or blood test (RAST)
Elimination diet and challenge protocol
Beings in infancy
Can begin any time throughout life
Eczema, vomiting, swelling, hives and anaphylaxis
Can affect any body system
Time after eating
Immediate, or seconds/minutes after
Minutes or up to 48 hours
Includes egg, milk, nuts and seafood
Natural or additive food chemicals
A few grams or less (traces and particles)
Can vary from a lot to a little
Reduced food chemical intake
Egg and milk allergies predictably fade but not and seafood allergies can persist
Unpredictably waxes and wanes
Airborne allergies (dust mite, animal dander, grasses and pollens)
Allergy and food intolerance can go hand-in-hand. Paediatrician Elizabeth Pickford sees this phenomenon often in her work. "Babies have immature body systems and this can make them particularly vulnerable," she says. And managing to keep food and life allergy-free can be extremely demanding on a family.
Fortunately, specialised baby formula is available but care is needed when you introduce solids into a sensitive baby's diet. The food needs to be bland and safe, and guidance from a dietitian with expertise in this area is recommended. Often many of these food problems resolve by the time the child is three years old.
Today the most commonly used allergy test is skin-prick testing, where a tiny droplet of an allergy solution (called the allergen) is place on the skin and gently, without drawing blood, pricked into the skin surface with a slightly pointy small blade called a lancet. If there is an allergy a small lump, like a mosquito bite, will flare within minutes.
Blood tests are also available. Known as radioallergosorbent tests (RAST), they measure circulating immunoglobulin E (IgE) - the allergy villain released by the immune system.
Food allergy is treated by avoiding the culprit food. Egg, milk, seafood, nuts and sesame are the most common problem foods. Wheat and soy can also cause allergies but these tend to be mild and transient. Egg is the most common allergy in children, and nuts are associated with the most severe reactions.
If a woman is breastfeeding a child with an allergy, she will also need to avoid the food because allergens can be transferred through breast milk. In this situation consulting a dietitian is a good idea so both mother and child are getting what they need nutritionally.
Immunotherapy (desensitisation) by injection or oral drops is available for hay fever and asthma when there are severe, difficult-to-manage symptoms, however there is little evidence that food allergy might be controlled in this way. The most important step is recognising where there is a strong family history of allergy. From birth to about the age of two years is when the immune system is developing rapidly, and a critical time for children at high risk of developing allergies. To minimise the risk, it's recommended mothers of high-risk babies don't eat nuts and eggs if breastfeeding, or use a specialised low-allergen formula. Maintaining a nut-free and seafood-free household for the first three years of the child's life may also help.
Is the problem gluten?
Some people have a condition known as coeliac disease where gluten (a protein found in certain grains) can cause damage to the lining of the intestine. It is inherited and affects about one in 100 Australians, and possibly more. It can be a serious illness or an innocuous problem that causes failure to thrive in children (from not absorbing nutrients), and symptoms such as bloating, cramps, diarrhoea and fatigue in adults.
Having coeliac disease means a strict and lifelong gluten-free diet, because gluten can be damaging to the gut whether there are symptoms or not. Left untreated there is a long-term risk of nutritional deficiency, osteoporosis and, for some, bowel cancers.
Screening blood tests are available but a definite diagnosis requires a small bowel biopsy (where a snippet of the bowel is taken). It's important that you don't change your diet until you are tested or you could get a false result.
Wheat allergy, which rarely occurs beyond infancy, is different from gluten intolerance.
The great range of gluten-free products now available includes pasta, breakfast cereals, breads, crispbreads and sweet biscuits made using maize, rice, soy, potato and tapioca flours. Gluten-free grains include millet, buckwheat, quinoa and amaranth.
What about lactose?
Lactose is a sugar found in all animal milks, including human breast milk, and lactase is the enzyme that breaks it down. Most of us are born with lactase, though rarely some newborns may lack the enzyme. Those of us who have lactase will tend to lose the enzyme unless dairy products are regularly eaten. However, in some cases where dairy products are being consumed, the amount of lactase produced after weaning may drop to very low levels, resulting in primary lactase deficiency. This normally becomes apparent after the age of two.
Secondary lactase deficiency occurs when the gut is temporarily stripped of lactase after being damaged by a severe bout of gastroenteritis, malnutrition, or uncontrolled coeliac disease. The symptoms disappear when the intestinal wall has recovered, usually within two to four weeks.
Both primary and secondary lactase deficiency can result in lactose passing through the gut undigested, causing discomfort, nausea, tummy bloating, flatulence and diarrhoea.
In the past, it was assumed babies who could not tolerate milk were lactase-deficient. Now we know the reaction from milk may in fact cause the lactase deficiency. So if you are told you or your baby has lactase deficiency, be prepared to question the diagnosis and investigate the possibility of food sensitivity.
Living with an allergy or intolerance
If you or your child has recently being diagnosed as having a food allergy or intolerance, life will be easier if you are prepared. It's a good idea to:
read food labels
discover Orgran and other healthy brands at your local supermarket
spend some time browsing through a health food shop
always have an emergency snack with you in your bag
join a support group online
be alert and assertive when eating out.
Understanding the differences between food allergy and intolerance is important because they need to be approached in different ways. Get guidance and support from experts rather than self-diagnosing (or relying on information from the internet, which is often incorrect).
A good starting point is to check out the many low-allergen foods available from supermarkets and health food stores and read our comprehensive article The truth about food labels, so you know exactly what you're eating.
Research into diagnosing and managing allergies and intolerances is always ongoing, so subscribe to a good information source and stay in the loop!
Try this low-allergen cupcake recipe for a milk-free, egg-free, gluten-free, soy-free, nut-free and low-chemical additive treat.
1 cup sugar1/2 cup (125g) Nuttelex margarine3 tablespoons puréed pear1/2 teaspoon vanilla extract1 1/2 cups gluten-free plain flour1 3/4 teaspoons gluten-free baking powder1/2 cup watergluten-free icing sugar, for dustingStep 1 Line cupcake pan with patty cases and set aside.
Step 2 In a medium bowl, beat sugar and margarine until well combined. Add puréed pear and vanilla extract and mix well. Stir through the flour and baking powder. Stir through the water until mixture is smooth.
Step 3 Spoon into patty cases until each is 2/3 filled. Bake for 20-25 minutes or until golden and cupcakes spring back when lightly touched.
Step 4 Set aside to cool, then dust with icing sugar before serving if desired.
Natural chemical allergy culprits
Salicyates: these are responsible for the tartness of most fruit, veg, herbs, spices, tea and honey, and are also found in perfumes and some medications.
Amines: these give some foods a rich flavour as they develop - that's why bananas and avocadoes taste better as they ripen. Also found in chocolate, cheese, canned fish and leftover meat dishes.
Glutamates: these are found in savoury foods such as soy sauce, nori, tomato, mushrooms and parmesan cheese.