Some people are sensitive to particular foods like nuts, shellfish and cereals. The symptoms of food allergy can include breathing problems, stomach upsets and skin rashes. They are caused by an immune system response or a chemical reaction in the body. Some severe food allergies can be life threatening. Professional diagnosis is important, because other medical conditions may share the same symptoms.
Most reactions to food are actually food intolerance. About one in 20 children and one in 100 adults have food allergies.
Allergy is on the increase
Allergies in general are on the increase worldwide and food allergies have also become
more common, particularly peanut allergy in preschool children. About 60 per cent of
allergies appear during the first year of life. Cow’s milk allergy is one of the most common in early childhood. Most children grow out of it before they start school.
Food allergy can be inherited
Children who have one family member with allergic diseases (including asthma or eczema) have a 20-40 per cent higher risk of developing allergy. If there are two or more family members with allergic diseases, the risk increases to 50-80 per cent.
Allergy is an immune response
Allergies are an overreaction of the body’s immune system to a specific part of a food,
usually a protein. These proteins may be from foods, pollens, house dust, animal hair or
moulds. They are called allergens. The word ‘allergy’ means that the immune system has
responded to a harmless substance as if it were toxic.
Food intolerance is a chemical reaction
Food intolerance is a ‘chemical’ reaction that some people have after eating or drinking
some foods; it is not an immune response. Food intolerance has been associated with
asthma, chronic fatigue syndrome and irritable bowel syndrome (IBS). Food intolerance is much more common than food allergy.
Symptoms can be similar
It can be difficult to tell the difference between the symptoms of food allergy and food
intolerance. Usually symptoms caused by food allergy develop very soon after consuming the food but, while symptoms caused by food intolerance can be immediate, they may also take 12-24 hours to develop. Food intolerance reactions are usually related to the amount of the food consumed. They may not occur until a certain amount (threshold level) of the food is eaten, but this amount varies for each person.
The symptoms of food allergy and intolerance can also be caused by other conditions, so it’s important to see your doctor for a medical diagnosis.
Symptoms of food intolerance
Symptoms of food intolerance can include:
· Nervousness, tremor
· Rapid breathing
· Headache, migraine
· Burning sensations on the skin
· Tightness across the face and chest
· Breathing problems – asthma-like symptoms
· Allergy-like reactions.
Symptoms of food allergy
The symptoms of food allergy can be life threatening. Common symptoms include:
· Itching, burning and swelling around the mouth
· Runny nose
· Skin rash (eczema)
· Hives (urticaria – skin becomes red and raised)
· Diarrhoea, abdominal cramps
· Breathing difficulties, including wheezing and asthma
· Vomiting, nausea.
Affected body parts
Various sites on the body can be affected by an allergic reaction to food, including:
· Eyes – itching, watering
· Nose – stuffiness, sneezing
· Mouth – itching, swelling
· Throat – swelling
· Digestive system – stomach pains, vomiting, diarrhoea
· Skin – rashes, such as hives (urticaria) or atopic dermatitis
· Lungs – asthma, more common in children than adults
· Central nervous system – headache, irritability, fatigue, convulsions.
Anaphylactic shock is life threatening
Anaphylaxis, or anaphylactic shock, is a severe allergic reaction that needs urgent medical attention. Peanuts, other nuts, insect stings and some medicines are the most common allergens that cause anaphylaxis. Within minutes of exposure to the allergen, the person can have potentially life-threatening symptoms, which include:
· Difficult or noisy breathing
· Swelling of the tongue
· Swelling or tightness in the throat
· Difficulty talking or a hoarse voice
· Wheeze or persistent cough
· Loss of consciousness or collapse
· Becoming pale and floppy (in young children).
Several factors can influence the severity of anaphylaxis, including exercise, heat, alcohol, the amount of food eaten, and how food is prepared and consumed.
To prevent severe injury or death, a person with anaphylaxis requires an injection of
adrenalin. Injections of adrenaline, which can be given by the person themselves or their family or carier, are available on prescription or directly from a pharmacy.
Food allergy – common causes
Nuts, eggs, milk or soy cause about 90 per cent of food allergies. Peanut allergy is one of the most common allergies in older children. These foods commonly cause allergies:
· Other nuts
· Grains such as rye, wheat, oats
· Molluscs such as oysters, mussels, clam, squid and octopus
· Crustaceans such as lobster, prawn, crab, shrimp
· Fruit, berries, tomato, cucumber, white potato or mustard
· Food additives like benzoates, salicylates, MSG and sulphite derivatives.
Food intolerance – common causes
The foods that tend to cause intolerance reactions in sensitive people include:
· Dairy products, including milk, cheese and yoghurt
· Eggs, particularly egg white
· Flavour enhancers such as MSG (monosodium glutamate)
· Food additives
· Strawberries, citrus fruits and tomatoes
· Wine, particularly red wine
· Histamine and other amines in some foods.
Finding the allergen
When symptoms appear within a few minutes of eating the particular food, this makes
pinpointing the allergen an easy task. However, if the cause is unknown, diagnostic tests
may be needed such as:
· Keeping a food and symptoms diary to check for patterns.
· Removing all suspect foods for two weeks, then reintroducing them one at a time to test
for reactions (except in cases of anaphylaxis). This must only be done under medical
· Skin prick tests using food extracts.
· Blood (RAST) tests.
Avoiding the food
The easiest way to treat a food allergy or intolerance is to eliminate it from the diet.
Sometimes, the body can tolerate the food if it is avoided for a time, then reintroduced in
small doses, particularly in food intolerances. Before you eliminate foods from your diet,
seek advice from a doctor and dietician.
Preventing food allergy in children
Allergy prevention in children is an active area of research. Findings to date indicate that:
· Prenatal – there is no conclusive evidence that avoiding allergens in pregnancy will help
prevent allergies in your child.
· Postnatal – exclusive breastfeeding during the first four to six months appears to protect
against the development of allergies in early childhood. Exposure to cigarette smoke and
starting solids early can increase the risk of developing allergies in early childhood.
· Breastfeeding – if a baby is known to be allergic to a particular food, a breastfeeding
mother should avoid eating that food.
· Soy formula – studies have shown that using soy milk formula does not prevent the
development of allergies in children.
· Partially hydrolysed formula – these are cow’s milk based and have been processed to
break down most of the proteins that cause symptoms in infants who are allergic to
cow’s milk. They reduce the risk of developing eczema and cow’s milk allergy in infancy
and early childhood.
To avoid allergic foods, learn the terms used to describe these foods on food labels, for
· Milk protein – milk, non-fat milk solids, cheese, yoghurt, caseinates, whey, lactose
· Lactose – milk, lactose
· Egg – eggs, egg albumen, egg yolk, egg lecithin
· Gluten – wheat, barley, rye, triticale, wheat bran, malt, oats, cornflour, oatbran
· Soy – soybeans, hydrolysed vegetable protein, soy protein isolate, soy lecithin
· Salicylates – strawberries, tomatoes.
Milk and other dairy products contain a sugar or carbohydrate called lactose. Normally, the
body breaks down lactose into its simpler components with the help of the enzyme lactase.
Most mammals stop producing lactase when they are weaned; humans, however, continue
to produce it throughout life. Without enough lactase, a person can have digestive problems
like abdominal pain and diarrhoea. This is known as lactose intolerance or lactase
Managing lactose intolerance
Most people with lactose intolerance can handle small amounts of lactose, such as a glass
of milk. However, the following tips may help:
· Try cheese and yoghurt; they are generally better tolerated than milk.
· Drink full fat milk because the fats slow the journey of the milk through the intestines and
allow the lactase enzymes more time to break down the sugars.
· Avoid low fat or non-fat milks – they travel quickly through the gut and tend to cause
symptoms in lactose intolerant people. Also, many low fat milk products may contain
skim milk powder, which provides a higher dose of lactose.
· Don’t give up milk products entirely. They are very nutritious.
· Drink milk in moderate quantities. Most people with this condition can tolerate 240ml of
milk per day, but you need to be work out your own tolerance level. You can buy milk
that has had the lactose broken down, which makes it lactose free.
· Have moderate amounts of dairy foods. Most people can tolerate the amount of lactose
– Half a cup of full cream milk
– Three-quarters of a cup of ice-cream
– Three-quarters of a cup of yoghurt
– Half a cup of white sauce
– Three-quarters of a cup of un-ripened cheeses like cottage or ricotta.
· Eat fermented milk products like some yoghurts, mature or ripened cheeses (like
cheddar, feta and mozzarella), and butter – they usually don’t cause problems.
· Eat foods that contain lactose in combination with other foods or spread them out over
the day, rather than eating a large amount at once.
· Use heated milk products like evaporated milk; they seem to be better tolerated because
the heating process breaks down some of the lactose to glucose and galactose.