The amount of information (and misinformation) about food allergies and intolerances can be confusing, not to mention dangerous. Dietitian Jane Dostine has a simple guide to the most common food allergies, how to recognise a food reaction and, most importantly, how to prevent them from occurring.
For some people, food can cause distressing, even dangerous, reactions or chronic ill health. Since different food problems require different management strategies for avoidance, it is important to identify and distinguish between food reactions that are life-threatening, and those that are more of an inconvenience.
What’s the difference between a food allergy and food intolerance?
A food allergy involves an immune response where the immune system recognises an ordinarily harmless substance (a specific food protein) as dangerous. A food intolerance, however, does not involve the immune system at all – it may be the irritation of nerve endings in different parts of the body that leads to reactions.
Severe allergic reactions
Allergy symptoms may begin with sudden itching of the eyes or face and within minutes progress to more serious symptoms, including:
Difficulty and/or noisy breathing
Swelling of the tongue
Swelling or tightness in the throat
Difficulty talking or hoarse voice
Wheeze or persistent cough
Loss of consciousness and/or collapse
Pale and floppy
Dizziness or confusion
Nuts are the most highly allergenic food, with peanut allergies affecting 1 in 50 children. Two-thirds of children with a nut allergy will be allergic to one or more tree nuts (cashews, hazelnuts, almonds, walnuts, Brazil nuts, pecans, pine nuts, pistachios and macadamia nuts), and any nut allergy can be just as severe as another. This allergy tends to persist into adulthood, with about 1 per cent of Australian adults having a nut allergy.
Complete avoidance is vital, as even a miniscule amount may trigger a reaction. Reactions can also occur from touch and inhalation. Make sure there is no cross-contamination from other nut-containing foods and examine all food labels closely, as well as body lotion labels for nut oils.
Symptoms can include cramps, vomiting, diarrhoea, facial swelling, wide-spread hives and/or breathing difficulties (see 'Severe allergic reactions', below). In the worst case, anaphylaxis (the most dangerous form of an allergic reaction) can occur. This is a rapid, whole body response where there is a sudden serious drop in blood pressure.
Peanuts are the food most likely to cause anaphylactic reactions. As tree nuts are widely available and used more often in various foods and recipes, these allergies are on the increase. Ongoing exposure to nuts, even in small amounts, means less and less exposure is needed to cause a reaction. Complacency can have fatal consequences.
A dairy allergy is a reaction to cow’s milk protein, seen in infants and toddlers, and should not be confused with other adverse reactions to milk, like cow’s milk intolerance (see over). Milk, dairy products and foods containing milk as an ingredient need to be avoided. Highly allergic children will react to traces of milk. Milk has been implicated in 1 in 5 of all childhood food allergies, but most children grow out of this one.
Stay away from cow’s milk, dairy products and foods or dishes where milk is an ingredient, such as baked goods, chocolate and even savoury foods that contain milk, like luncheon meats and flavoured crisps. Also avoid baby foods fortified with milk powder. If you are breastfeeding, you will need to discuss adjusting your diet with your doctor or an Accredited Practising Dietitian.
Most milk-allergic infants will have eczema, starting from 4–6 weeks of age. Exposure to milk protein through breastfeeding can irritate the gut, resulting in poor growth. Ingestion can cause acute onset of hives, vomiting, diarrhoea or possibly anaphylaxis.
Fatal reactions are unusual. The gravity of this allergy lies with the serious nutritional deficiencies that can arise. Use dairy alternatives or specialized infant formula to ensure your child receives adequate calcium, minerals and vitamins. Ask your doctor or dietitian for recommendations.
Milk intolerance occurs when the sufferer reacts to cow’s milk (not to be confused with the milk sugar, lactose) and it often starts in the first weeks of life resulting in an irritable, colicky baby. It is commonly associated with other intolerance reactions to soy and food chemicals (naturally found in fruit and vegetables). Children with a milk intolerance may tolerate milk as they get older (but often refuse to drink it in quantity).
Unlike an allergy, intolerance is a dose-related issue – meaning the more you have, the more likely a reaction. The very sensitive may need to be strict about avoiding milk products, but most adults can tolerate some milk. Cow’s milk-based infant formula, milk, dairy products and milk in food products or dishes can be a problem.
Gut symptoms like bloating, diarrhoea, constipation, and irritable bowel, or respiratory congestion. Infants can have mucous and specks of blood in their stools, reflux or nappy rash.
Gut irritation can be so severe in babies with milk intolerance that anaemia and poor growth can be consequence – these babies will need specialised infant formula. Kids and adults who don’t drink milk should incorporate calcium-fortified dairy alternatives to ensure nutritional adequacy.
Lactose intolerance occurs in people who have a problem digesting the milk sugar lactose, because they are deficient in lactase (the enzyme required to digest lactose). Lactase deficiency can occur as a secondary problem to chronic gut disorders, and is more prevalent in some ethnic groups such as Aboriginal, African, Asian, Mediterranean and Middle Eastern.
Lactose is found in milk and products containing milk or milk powder, yoghurt, ice-cream and many medications. However, most people with lactose intolerance can tolerate small quantities of milk, yoghurt and low-lactose foods, like cheese. In fact, while there is a wide variation in tolerance, research has shown that the majority of lactose-intolerant people can tolerate about a cup of milk each day.
When the undigested lactose gets through to the large bowel it is fermented by bacteria, and this will cause symptoms of abdominal discomfort, bloating, excessive wind and diarrhoea about an hour or two after ingesting lactose.
Lactose intolerance is usually a mild inconvenience, however, to ensure calcium intake remains adequate, look for lactose-free milk or other dairy alternatives, like fortified soy or rice drinks.
The most common food allergy in infants and associated with infantile eczema, egg allergy is likely to fade after three years of age.
Reactions can happen to whole egg and ‘eggy’ foods, like omelettes, quiche and meringue and foods where egg is used as an ingredient, such as cakes, mayonnaise, egg noodles, ice-cream, sorbets and egg wash on buns. Some children may also react to traces of egg.
First reactions often happen with the introduction of baby egg custard, causing hives around the mouth and vomiting. Though rare, some infants and children can have an anaphylactic reaction to egg. Older children might still get skin contact reactions or respiratory symptoms. Adults may not like egg, but can generally manage egg as an ingredient.
The reaction can range from mild to dangerous. For those especially sensitive to eggs, egg fumes, getting egg on the skin or smelling egg on a person’s breath can be a problem. Raw egg is more potent than cooked egg, so don’t lick the beaters!
A seafood allergy can develop at any time of your life, and can be tough if somebody in the family loves to eat, catch or cook seafood.
A fish allergy can be specific to one fish or across all types, with the big fish – cod, ling, barramundi and snapper – generally the cause of most fish allergies. Very sensitive people can even be allergic to tinned tuna. Shellfish allergies tend to apply to all crustaceans, and some people can be allergic to squid or octopus.
Reactions vary from mild – watery eyes or violent vomiting – to severe asthma or collapse. Once sensitised, this allergy tends to be for life.
Touching seafood or breathing cooking seafood fumes can provoke a reaction. Walking on a wharf where people fish, or visiting the aquarium, can also be hazardous.
A soy allergy, usually seen in young children with infantile eczema, is relatively uncommon compared with egg, milk and peanut allergies. It usually resolves in the early years and is not seen in adults. While soy allergy subsides, the more common soy intolerance may still affect some children and food-sensitive adults.
Soya beans are used widely in the food industry, so it is important to always read labels carefully. Stay away from soy drinks and soy products, such as soy flour, beans, sprouts and tofu. Soy lecithin (a type of fat extracted from soy beans that is used as an emulsifier in foods like margarine or salad dressing) seems to be generally well tolerated.
Symptoms can include eczema flare-ups, itching and tingling of the mouth and lips, hives, vomiting or diarrhoea. Some children will have a more severe reaction and go into anaphylactic shock.
In general, the amount of food needed to trigger an allergic reaction is much higher for soy than other allergenic foods, so soy-allergic children are at less risk of an allergic reaction to traces of soy in food products.
Wheat intolerance, which often occurs in people with a family history of irritable bowel, is a dose-related problem with wheat and sometimes other gluten-containing grains, like rye.
Avoiding wheat and other gluten-containing grains
Steer clear of wheat, barley, rye and oats, although oats and rye may be better tolerated than wheat. Because these grains all contain gluten, sensitive people may best manage their symptoms with a gluten-free diet, while others can get away with a little bit.
Symptoms vary from loose stools to constipation and bloating, and central nervous system symptoms like clouded thinking. Infants can be irritable and experience reflux.
Though inconvenient, there is no gut damage with this problem, though you should be checked by your GP to exclude coeliac disease. To avoid compromising calories and nutrients, use a variety of other grains to meet your needs.
This is not a common allergy and is usually seen in infants who have several other food allergies. It usually resolves quite early, at about two years of age, and is generally not seen in adults.
Specifically, wheat and wheat products need to be avoided. This includes breads, cakes, breadcrumbs, pastry, pasta, biscuits, breakfast cereals and flour. Alternative names for wheat include burghul, farina, kamut, matzo, spelt, triticale, malt, couscous and semolina.
Children will mainly experience eczema, although sometimes more severe allergic symptoms can occur (but rarely anaphylaxis).
Wheat allergy is considered to be a relatively weak allergy, so although wheat should be avoided, extreme avoidance measures are generally not considered necessary.
In people with coeliac disease, their immune system reacts abnormally to gluten (found in wheat, rye, barley) and oats, causing damage to the lining of the small bowel.
Since coeliac disease is a permanent gut reaction to dietary gluten, a life-long gluten-free diet is necessary for gut integrity. Stay away from gluten and hidden gluten in products like wheat starch and maltodextrin (wheat) found in processed meats, burgers, sausages, sauces, gravies, marinades, surimi, cornflour, soy sauce, soups, spices and stock cubes. A gluten-free statement on food labelling can help you make a safe choice.
Possible symptoms include constipation, fatigue, headaches, abdominal cramping, bloating, diarrhoea, low blood iron, miscarriages or bone fractures. Keep in mind that these symptoms are common to other conditions, so further testing and investigation may be needed.
NOTE: If you think you may have coeliac disease, it’s important to talk to your doctor or dietitian – you will need to be tested before amending your diet to exclude gluten.
Over time, failure to adhere to a gluten-free diet can lead to anaemia, decreased bone density and an increased chance of developing malignancies of the intestine and lymphoid system.
Food chemical intolerance
Food chemicals can be naturally occurring – such as salicylates, amines and glutamates – or added, like flavour enhancers, preservatives and colours. This type of intolerance does not involve the immune system and can be a problem across all ages.
Avoiding food chemicals
There is a dose effect, which means the more sensitive you are, the less you are able to tolerate. Chemicals are found in a diverse range of foods, and vary in composition. Sometimes reactions to additives are easier to identify since the particular chemical causing you grief is more highly concentrated in processed foods. If you can’t work out which chemicals and foods are causing the problem, it might be worth trialling an elimination diet – but only under the supervision of a dietitian.
A reaction can be immediate or delayed, with symptoms ranging from skin reactions (hives and rashes) to gut problems, mucous, headaches or vague symptoms of aches, pains and feeling unwell. Children can be irritable and restless, and kids with ADHD can become more hyperactive and impulsive. Babies can be unsettled, colicky and get bad nappy rash.
While frustrating, it’s not usually dangerous, unless a food chemical is a trigger for asthma or an anaphylactoid reaction (a reaction that looks like anaphylaxis). However, avoiding food chemicals can mean excluding a wide range of foods, or even a whole food group, and this could mean a gap in nutritional adequacy. To explore a food chemical intolerance, seek advice from an Accredited Practising Dietitian.
Fructose (fruit sugar), oligosaccharides (simple sugars linked together) and lactose (milk sugar) are all fermentable sugars that get digested in the gut. If excess fructose, lactose overload or too many oligosaccharides move through the gut and into the large bowel, then wind and a bit of tummy discomfort will occur in most people.
Avoiding fermentable sugars
Fructose is found in fruit, honey and juices. Oligosaccharides are in wheat, rye, some vegetables and legumes. Lactose is in milk, yoghurt and ice-cream. A reduced intake might help settle gut symptoms.
Increased flatulence, and people with a sensitive gut condition – like an irritable bowel – may experience an exacerbation of symptoms with excessive wind, bloating, stomach pain and a change in frequency and texture of bowel movements.
Passing wind is normal, and a sign that you have a healthy gut. While it can be a little embarrassing at times, this problem is mostly inconvenient, especially if you have a sensitive gut. It would be worth a visit to a dietitian to work out which foods are causing the trouble.