An allergy is caused by an improper, exaggerated response of the body’s immune system. Our immune systems usually keep us healthy by fighting germs that cause disease. But if you have a food allergy, your immune system sees a particular food as the enemy. The food that causes a reaction is called an allergen and your body attacks it as if it were a bad germ. The attackers are called antibodies. They cause chemicals to be released in an unnecessary attempt to rid the body of the offending substance. Unfortunately for the allergy sufferer, the effect of the chemicals can cause swelling and irritation, as well as other symptoms, in certain parts of the body.

What are the symptoms of food allergy?

Symptoms can range from mildly uncomfortable to life-threatening. Some people have reactions to food within minutes, while other reactions may not occur for hours. In general, the more severe the allergy, the quicker the response. The most common symptoms are:

Respiratory system: stuffy or runny nose, itchy eyes, asthma, throat swelling.
Skin: itching, rashes, hives, eczema and swelling, especially around the mouth and face.
Digestive system: diarrhea, constipation, nausea, vomiting, bloating, stomach pain.
Other: anaphylaxis (sudden severe reaction involving many body systems), failure to thrive, headaches, paleness, dark circles under the eyes.

A food intolerance is not the same as an allergy and does not involve the immune system. A food intolerance is a general term to describe a variety of reactions to a food or food additive. For instance, you may have some abdominal discomfort from lactose in milk or the fibre in cereals. The symptoms have a wide range of description of severity. Other medical conditions can cause some of the same symptoms as food allergies and intolerances. It is often difficult to define the cause of these symptoms. See your doctor for a proper diagnosis.

How is a food allergy diagnosed?

Diagnosis of food allergies can often be a challenge. Sometimes, it can be as simple as removing a suspect food from the diet to see if symptoms improve. Other times, the food allergy may not be as obvious or may involve many foods or factors in the environment, making diagnosis difficult.

If you think you have a food allergy, first visit your doctor, who may rule out other possible causes of your symptoms. Keep a diary of what you eat and drink and all medications you take. Record any reactions. This information will help the doctor decide if you need a referral to an allergist for further tests.

To confirm allergic reactions such as hives (urticaria) an allergist often does a skin or 'prick' test. Tiny amounts of the suspected or most common allergens are inserted or scratched under the skin. If the area comes up in a bump with an area of itchy skin around it, an allergic reaction has occurred. Sometimes a skin prick test will not give a clear response. For patients with serious allergic reactions, a blood test may be used. This is a safe way to determine allergy but it is less accurate than skin testing.

Your doctor may suggest an elimination and challenge diet to help diagnose the allergy. In this diet, the suspect food is avoided until the symptoms disappear, about five to 10 days. The food is then slowly added back to see if a reaction occurs. A strict elimination diet is usually limited to no longer than two weeks, and is usually planned with the help of a registered dietitian.

What are the most common food allergies?

The most common culprits are cow’s milk, eggs, nuts, peanuts, fish and shellfish. Other common food allergens are wheat, tomatoes, strawberries, oranges and soya bean. The degree of a reaction can vary. Some people are so sensitive that skin contact or even the smell of the food is enough to trigger a serious reaction!

Those with less severe allergies may be able to eat food in small quantities on an occasional basis. Some raw foods that cause a reaction may be tolerated when cooked, as cooking sometimes changes the protein. This is not the case with fish, nuts or peanuts, which should be avoided in any form if they are known to cause an allergic reaction.

Some food additives may cause reactions. The reaction may be a food intolerance or an allergy. Food additives are used as preservatives, coloring agents and to improve taste and quality in commercial foods. Since additives are used so often, they may present problems to those who are sensitive. Eating a well balanced diet while avoiding large amounts of refined or processed foods will help you to avoid an excess of additives. A very restricted diet is not usually necessary except for those who are extremely sensitive.

How do I treat my food allergies?

Be vigilant. Avoid the foods causing your allergic reactions. However, this is sometimes easier said than done! Often, forms of the food may be found in products without being obvious. For instance, caseinate is added to many commercial products - who would guess that it is a milk protein and can cause problems for people with a milk allergy!

For those with food allergies, label reading becomes a way of life. Product labels should be checked before each purchase, as manufacturers may change ingredients. It is important that you control your allergies yet maintain a well-balanced diet, particularly if many foods are restricted.

Medications may also contain ingredients to be avoided. Your pharmacist can help you decide if the products are safe for you or not.

Can food allergies be prevented?

The last trimester of pregnancy and the first months of life are thought to be critical periods for developing food allergies in babies. If there is a family history of allergies, diet during pregnancy and while breastfeeding can affect the infant. A pregnant mother with a family history of allergies should avoid the foods to which she is allergic and may want to reduce her intake of the most highly allergenic foods during the last trimester.

Breastfeeding for at least the first six months and as long as possible is also suggested. However, food allergens can be passed into the breast milk so a breastfeeding mother should still be careful with her diet. A well-balanced diet is important for both mother and baby. If the mother’s diet is restricted, nutrient supplements may be required.

Delaying the introduction of solid foods until six months of age, and avoiding highly allergenic foods for the first year may be helpful. Starting solid foods one by one every two to three weeks and watching for reactions can also help to detect food allergies.

A special word about peanuts . . .

Growing numbers of people are allergic to peanuts, and this allergy can be a dangerous one. Peanuts are thought to be one of the most common foods to cause a serious allergic reaction. Even a small amount, skin contact or the smell of a peanut can be life threatening to those at risk.

For prevention, it is suggested that children with a family history of allergies avoid peanuts and peanut products for at least the first three years of life. A peanut allergy is thought to last a lifetime, and is not likely to be outgrown.

Peanuts are legumes, and not related to nuts that grow on trees. A person with severe peanut allergy should avoid all sources of peanuts or peanut products. Labels on commercial products should be checked carefully. Contamination can occur in processing and in bulk food containers, so caution is advised. These people may also have other legume allergies.

Where can I get help and information?

While dealing with food allergies can be frustrating and challenging, there are people who can help you. First, proper diagnosis and a recommended treatment plan by your doctor are essential. There are registered dietitians in hospitals and private practice who can help you manage your food allergies. They can provide you with information as to what foods should be avoided as well as suggestions to help you maintain a balanced diet. There are also community groups that offer information and support for those with allergies. You do not need to suffer alone - help is available.

Food Allergies Handling what can be a life-threatening condition

Do you or any members of your family have a food allergy? If so, you probably stand in the aisles of the supermarket reading ingredient lists to learn if a food is safe to eat.

What exactly is an allergy?