Food allergies

Food allergies

What is a food allergy?

Food allergy is an abnormal response to food that is triggered by a specific reaction in the immune system and causes various symptoms in the skin, digestive and respiratory systems.

Although the symptoms of food intolerance resemble those of food allergy, they are very different. There is a general perception that food allergies are common. However this is untrue, with only about 1% of adults having clinically proven allergic reactions.

True food allergies can result in catastrophic reactions and avoidance of the trigger food is imperative.

What causes food allergies?

Any food can cause a food reaction, with fish, shellfish, shrimp, lobster and peanuts, among the most common food allergies in adults. Milk, eggs, soy and peanuts can trigger allergies in children.

The resistant proteins in the food are what cause the reaction. They resist heat in cooking, the stomach acid and the digestive enzymes. These resistive proteins enter the bloodstream, targeting organs, causing allergic reactions throughout the body.

What are the signs and symptoms of food allergies?

Symptoms of food allergies occur within a few minutes to an hour of eating. They include:

  • An itching of the mouth.
  • Difficulty in swallowing and breathing.
  • Feelings of nausea, vomiting, diarrhoea and abdominal pain.
  • Hives and eczema visible on the skin.
  • Coughing, sneezing and wheezing may be experienced.
  • Feelings of light-headedness and weakness.
  • In severe cases anaphylaxis (a drop in blood pressure) may occur, which requires immediate medical attention.
  • Occasionally, although not as frequently, migraine headaches, colitis or malabsorption occurs. These reactions are referred to as food intolerances or sensitivities as they don’t result from a true "allergic" response.

How are food allergies treated?

Medication can be taken after a person accidentally eats a triggering food. However there are no oral or injectable medications to prevent food allergies prior to consumption.

People who have experienced anaphylactic reactions to a food should wear a medical alert bracelet or necklace, stating which food allergies they have.

Those who experience anaphylactic reactions should carry a syringe of adrenaline, and seek immediate medical assistance.

How are food allergies diagnosed?

A family history can help determine predisposition to food allergies. A person with two allergic parents is more likely to develop food allergies than someone with one allergic parent.

A skin test or a double-blind placebo control food challenge can determine the cause of the reaction. The skin test involves pricking the skin with a solution of the suspected food. A small hive appearing on the skin may indicate an allergy. The double-blind placebo control food challenge, is where capsules of the suspected food and ‘dummy’ capsules are given and the reaction observed.

Blood tests may be used to investigate if a person has an allergy to a certain food, which measure the presence of food-specific IgE in the blood of patients. However these tests tend to be more expensive than other types.

How can I reduce the risk of food allergies in my children?

Look at your family allergy history, so that you can be prepared to recognise the signs. If your family is predisposed to allergies, you should follow these measures for your baby:

  • Resist introducing solid foods until the child is six months old.
  • Breastfeed for the first year, where possible.
  • Gradually introduce new foods, allowing a substantial period to pass, so that reactions may be monitored.
  • Wait until the child is one before introducing cow's milk.
  • Avoid feeding children peanuts until they are of school-going age. Peanuts should also be avoided in pregnancy and while breastfeeding. Note ingredients in biscuits and breakfast cereals where peanuts are frequently included.
  • Allergies in babies do not cause the usual signs such as hives, but can cause infantile colic (wind in the intestine associated with feeding difficulties) and poor growth. Infantile Colic causes the child to constantly cry and sleep poorly at night. An allergy to milk or soy can be a factor.

Can you suddenly become lactose intolerant after years of drinking milk and eating milk products?

Lactose intolerance is caused by a deficiency of lactase, an enzyme found in the wall of the intestine which breaks down lactose. Because lactose is the principal sugar found in milk, people with this problem cannot digest dairy products. People who have this problem will have abdominal cramps, bloating and diarrhoea after they eat dairy products.

The problem seems to be hereditary, but symptoms may not occur until puberty or late adolescence.

Acquired lactose intolerance can occur at any age in the context of intestinal diseases, such as viral or bacterial infections or other problems affecting the intestinal wall. Symptoms of lactose intolerance include cramps, gas, bloating or diarrhoea within 15 minutes to three hours after consuming milk or milk products. Transient lactose intolerance may occur after a bout of gastro enteritis. You should however consult a doctor to rule out other similar conditions.

Back to top of page