Intolerance or allergy

Many of us have allergic reactions to food or other substances. These reactions can range from mild to very severe – some are even life-threatening. However, true allergies are relatively rare and what many people consider to be allergies are really intolerances. So what is the difference between an allergy and intolerance?

A true food allergy is an almost immediate adverse reaction resulting from the body’s immune system to a particular food or component of a food, usually a specific protein.  Reactions happen quickly, usually within 30 minutes and always within two hours.

By contrast, food intolerance is more common and usually less severe, involving reactions to food which are not related to the immune system.  Intolerance reactions to food chemicals, both natural and synthetic, can occur several days after the food has been eaten.

Food Allergy

For most of us, the naturally occurring proteins found in food are harmless and nutritionally important for body growth, muscle development and physical maintenance.  But in some rare instances a severe, life-threatening allergic reaction known as anaphylactic shock can occur.

The most common culprits for food allergy are: cow’s milk, eggs, peanuts, soy, wheat and, less commonly, shellfish.  An individual may be allergic to only one or two of these, but may be sensitive to very small, even trace, amounts. 

Although children don’t actually outgrow allergies to milk, eggs and wheat, by the age of five most have much reduced reactions or are free of reactions.  Peanut and fish allergies are more usually severe throughout life.

In more than 90% of cases, food allergy is associated with atopic eczema – a chronic, extremely itchy skin rash which can occur on the face, arms, legs and the rest of the body in severe cases. 

More marked reactions to food are usually obvious, occurring almost immediately.  Symptoms can be associated with skin (hives, rashes, eczema, dermatitis), stomach (nausea, vomiting, diarrhoea, cramps), respiratory (asthma, wheezing, rhinitis, bronchospasm) or other, such as anaphlyactic shock, hypertension or swelling of the tongue or larynx.

Food Intolerance

Dr Velencia Soutter, a paediatric allergy specialist with Sydney’s Royal Prince Alfred Hospital, explains that food intolerance is quite different to food allergy.  ‘Intolerance is usually caused by a reaction to natural food chemicals such as salicylates, amines and MSG, or added chemicals such as colours and preservatives.  Natural chemicals are present in varying amounts in all foods.’

She also says, ‘In many cases, reactions occur only after a lot of foods and/or drinks containing these chemicals have been consumed.  In a very sensitive people, the chemicals which build up in the body over a period of days or weeks can cause chronic or recurrent symptoms.

As a general rule, the tastier the food, the richer it is likely to be in these chemicals.  Intolerance reactions include hives and eczema, nausea, vomiting, pain and/or diarrhoea, breathing problems such as a runny or blocked nose, sinusitis or wheezing, or other symptoms including headache, muscle aches and pains and being generally irritable.

Dr Soutter says, ‘Identifying foods which are high in the particular food chemicals which affect you, will help you to minimise or eliminate them from your diet.’

COMMON ALLERGIES AND INTOLERANCES

Cows Milk

Cows milk allergy is an immune reaction to a protein in cows milk and may present with many symptoms: skin rashes, vomiting, diarrhoea, colic or breathing problems.  Intolerance to cows milk is a non-immune reaction to some part of cows milk, or cows milk formula.  Symptoms may be less severe than for cows milk allergy and usually involve vomiting and/or diarrhoea and being irritable.

Lactose Intolerance

Lactose intolerance is different from cows milk allergy or intolerance because only the gut is involved.  Lactose is the sugar found naturally in milk which is broken down to simpler sugars in the small bowel by the enzyme lactase. 

If there is not enough lactase, undigested lactose passes through to the large bowel where bacteria feed on the lactose, forming as and water.  Symptoms of lactose intolerance include frequent watery and frothy bowel motions and stomach pains.

Joy Anderson, a breastfeeding counsellor with the Nursing Mothers’ Association of Australia, says that irritable, colicky babies are sometimes called ‘lactose intolerant’. 

However, this is rarely the case unless the baby has recently had gastroenteritis, or in the case of a breastfed baby, is suffering from a food sensitivity to proteins in the breastmilk that are derived from the mother’s diet.

More commonly is the breastfed baby, too much milk, eaten too quickly, creates an overload of lactose in the baby’s digestive system, which mimics the symptoms of lactose intolerance.

Gluten Intolerance

Intolerance to gluten, the protein found in wheat, rye, barley and possibly oats, causes the lining of the small intestine to become swollen and inflamed leaving the sufferer unable to digest and absorb nutrients from the food they eat. 

Gluten intolerance is known as coeliac disease.  Symptoms include diarrhoea, fatigue, stomach bloating, cramps, anaemia, weight loss, constipation, flatulence, nausea and vomiting.  A strict life-long gluten-free diet is the only effective treatment.  Once gluten, which is present in hundreds of common foods, is removed from the diet, the digestive tract begins to heal.

Reducing the Risk

Allergies tend to run in families.  Children from allergic families may be less likely to develop allergies themselves if they are breastfed for the first twelve months, although this does not always make a difference.  Mothers should avoid the common allergic foods in their diet (eg dairy foods, egg, peanut and seafood) and not introduce these foods to baby in the first year.

Foods which are not likely to cause allergy can be given from about 6 months.  Start with rice, potato and pumpkin, apple and pear and gradually try other fruit, vegetables, chicken and cereals.  Leave wheat, beef, citrus and berry fruits until 9 months or so.  Make sure no-one smokes near your child.

Anaphylaxis occurs when the body reacts violently to a ‘foreign’ substance by releasing large amounts of histamine.  Histamine is a chemical in the body which allows blood vessels to open up, causing red, blotchy skin, swelling and itching.  Antihistamine drugs work by blocking the effects of histamine.

Typical signs of anaphylaxis are:

• Rapidly progressive swelling of the lips, face and/or eyes.
• Hives or welts spreading quickly over the body.
• Breathing difficulty caused by swelling of the tongue or throat, wheezing or asthma.
• Acute distress – the child may look very pale, anxious and agitated.
• Light-headedness or collapse – the child may become weak and floppy, may complain of feeling faint, or may lose consciousness.

The presence of any combination of these signs is an indication that emergency treatment, in the form of adrenaline, given as an injection into the muscle, is required.

NATURAL FOOD CHEMICALS

Salicylates – a family of plant chemicals found naturally in many fruits, vegetables, nuts, herbs, spices, jams, honey, yeast extracts, juices, tea and coffee, beer and wines.

Amines  - come from protein breakdown or fermentation.  Large amounts are present in cheese, chocolate, wines, beer, yeast extracts and fish products.  They are also found in certain fruits and vegetables, eg bananas, avocados and tomatoes.

Monosodium Glutamate – (MSG) is a building block of all proteins and is found naturally in most foods.  It enhances the flavour of foods, which is why foods rich in natural MSG are used in many meals, such as tomatoes, cheese, mushrooms, stock cubes, sauces, meat and yeast extracts.

No one food is enough to cause an immediate reaction.  Over time, a particular substance (like natural amines), occurring in small amounts in several foods, accumulates in the body.  The last food eaten, e.g. chocolate, causes the reaction because the accumulated amount has exceeded the body’s threshold for amines.

CASE STUDY

Seven-year-old Simone, a pale, thin asthmatic child, suffered almost constantly from nausea and headaches and never seemed to want to eat.  Suspecting intolerance to natural food chemicals, Simone’s GP and her mum Monica, put her on a strict chemical-free ‘elimination diet’ for a few weeks until her symptoms settled. 

This involved removing foods high in natural chemicals such as strawberries, green apples, sausages, cheese and orange juice and replacing them with foods low in natural chemicals, such as pears, rice, chicken and eggs. 

After several weeks on the elimination diet, Simone was gradually ‘challenge tested” with foods suspected of causing her reactions.  By studying her reactions to each food, her mother and doctor were able to work out her ‘threshold’ and to modify her eating plan accordingly.

A year later, Simone has gained weight, has a healthy appetite and is able to eat from a wide range of foods.  Simone recalls, ‘It was really horrible.  I had headaches and felt sick in the tummy nearly all the time.  Now I know what makes me feel sick so I don’t eat those things.  I’m much better now.’

By Monique Webber

Resources: 

‘Friendly Food’, Swain AR, Sydney, Murdoch Books (Written by doctors from the Royal Prince Alfred Hospital Allergy Unit).

‘Dealing with Food Allergy’, ‘Salicylates, Amines & Glutamate’ and ‘Elimination Diet Handbook’

Booklets available from RPAH Allergy Unit, 9-11 Layton Street, Camperdown NSW 2050. Ph 02 9515 3300. Fax 02 9519 8420. Email allergy@email.cs.nsw.gov.au or visit their website. 

‘Milk Allergy and Intolerance’

An information booklet produced by The Gut Foundation.

Anaphylaxis Australia is a support groups for families of children who have had food related anaphylactic reactions. Tel 02 9842 5988 or 1300 728 000. Email coordinator@allergyfacts.org.au.

The information provided in this article is intended as a guide only. Always consult your doctor if you or your child is suffering any medical complaint. Any websites referred to by Australian Family contain information moderated by government and medical institutions or organisations.
 

This article was first published in Australian Family Magazine, May 2000. Updated July 2009.