By Loraine Stern, MD with Dr Ricky Richardson What's the difference between a real food allergy and intolerance?

Feeding a picky toddler is difficult under any circumstances. Add to that food allergies or trouble digesting certain foods, and it becomes even harder. There is a difference between a real allergy, which is a serious medical problem, and intolerance, which is mostly inconvenient. Here is some help to sort them out and some guidelines to deal with them.

Food Allergy: Symptoms and Causes

Allergic reactions are triggered when the body starts making antibodies to proteins in foods. A severe allergic reaction, with difficulty breathing and even collapse and shock, can be a life-threatening emergency. One of my patients was so sensitive that she would have a severe reaction if the assistant used the same scoop to serve her sorbet as he did to serve ice cream for others. Fortunately, most allergic reactions are milder, with symptoms that may include hives and other red, spotty rashes, diarrhoea, vomiting, runny nose and wheezing.

Milk is the most common cause of allergic reactions in small children. About two or three out of every 100 children are affected by cows' milk allergy; almost 95 per cent outgrow this by the age of 4. The second most common are allergies to nuts, shellfish and egg white . Reactions to these foods are less likely to disappear as your child grows up, and may be lifelong problems.

Peanuts are another frequent cause of allergic reactions. They are not really nuts - they are legumes, like peas - so often children who are allergic to peanuts are not allergic to almonds, walnuts or other true nuts. Remember that children under 4 should not be given whole nuts because they cannot grind them adequately with their teeth. As a result, they can easily inhale pieces into the lungs and choke.

Food Intolerance: Symptoms and Causes

Intolerance of certain foods is a less serious but still uncomfortable problem. The most common type is lactose intolerance, difficulty digesting the natural sugar in milk. Wind, bloating and diarrhoea appear within 30 minutes to 2 hours of drinking milk. Lactose intolerance can begin at any age but is most common in children over 4 or 5. Children with true allergies usually cannot tolerate even a tiny amount of the offending food. Lactose intolerance, on the other hand, is not as absolute. Often milk products such as yoghurt or cheese cause no problems because the lactose has broken down in processing. Some children can drink a little milk but develop symptoms if they have too much.

Gluten intolerance, the inability to digest a protein found in wheat, can be serious. Thought to be an inherited immune problem in the intestine, it can interfere with the absorption of many nutrients and lead to poor growth and poor weight gain, diarrhoea or constipation, and irritability. Gluten intolerance may appear soon after you introduce wheat products such as cereal or bread into a baby's diet.

What You Can Do

If you suspect your child has an allergy or intolerance, consult your doctor who may suggest that you are referred to a paediatrician. Don't make your own diagnosis, as food allergies can be tricky. If your child turns out to have significant allergies, you'll need to become fully informed about the contents of processed foods. For example, sherbet and margarine contain milk protein, called casein, and your child should avoid foods with calcium caseinate or casein on the label. Gluten can be hidden in vanilla extract, hydrolysed vegetable protein and ketchup. You may need to consult a paediatric dietician to make sure your child maintains a fully balanced diet while following necessary restrictions.

Children who are lactose intolerant can drink lactose-free milk and dairy products or can take chewable lactase tablets to replace the missing enzyme. Make sure your child gets enough calcium in other forms if he cannot tolerate many dairy products. Calcium-fortified orange juice, for example, can substitute for some milk.

Carers, nursery school teachers and friends who feed your child should be aware not only of the allergy but of what to do if a reaction occurs. Your paediatrician may give you a prescription for a special "pen" containing adrenaline for immediate use in case of a severe reaction. Keep some of these pens in various places - in the car, at home, at nursery. Make sure everyone knows how to use them and replace them when they are past their expiry date.

Prevention Strategies

If allergies run in your family, your child runs a higher risk of having problems. Breastfeeding and avoiding wheat, egg whites, seafood and cows' milk products until a child is over a year old may help. In fact, breastfeeding itself appears to protect somewhat against milk allergy - another reason to consider prolonging breastfeeding for at least a year.