Describing food allergy: Symptoms, diagnosis and treatment

A food allergy occurs when the immune system responds defensively to a specific food protein that is not harmful to the body. When that food is first eaten, the immune system responds by creating specific antibodies. When the food is eaten again, these antibodies go into action, releasing large amounts of histamines, which work to expel the food protein from the body. Histamines can affect the respiratory system, gastrointestinal tract, skin, and cardiovascular system.

Food allergy affects an estimated 6 to 8 percent of children under age 3 and up to 3 percent of adults. While there's no cure, some children outgrow their food allergy as they get older.

What are the symptoms of a food allergy?
Symptoms of a food allergy can appear almost immediately or up to two hours after the food has been eaten. Symptoms include a tingling sensation of the mouth, swelling of the tongue and throat, hives, vomiting, abdominal cramps, difficulty breathing, diarrhoea, a drop in blood pressure, and loss of consciousness. Severe allergy reactions called anaphylaxis can result in death.

Which foods are responsible for allergic reactions?
There are six foods that cause most of food allergies in children. They are milk, eggs, peanuts, wheat, soy, and tree nuts. In adults, most of food allergies are caused by peanuts, tree nuts and fish.

How are food allergies diagnosed?
Your doctor can perform a skin test to determine which substances cause a reaction. The skin test involves applying a small amount of an allergen and then making a tiny scratch with a needle in your arm or back. The scratches that become red and itchy indicate which substances trigger a defensive response by your immune system.

Your doctor might also do a radioallergosorbent blood test (RAST) to check the number of antibodies produced by the immune system. Elevated levels of certain antibodies can identify particular food allergies.

How are food allergies treated?
The best way to cope with a food allergy is to strictly avoid the foods that cause a reaction. Mild reactions often will subside without treatment. For rashes, skin creams might ease discomfort, while antihistamines will help reduce itching, congestion, and other symptoms. For more serious reactions, corticosteroids such as prednisone will help to reduce swelling. In life-threatening situations, an epinephrine injection immediately begins reversing symptoms and is the only effective treatment option.

Living with food allergies
Once you and your doctor have determined which foods you should avoid, it is important that you maintain a healthy, nutritious diet. Ask your doctor to recommend foods that will provide you with the necessary nutrition. You should also be aware of the ingredients in processed foods.

If you are prone to allergic reactions, you should always be prepared. Carry an epinephrine injection kit with you at all times.

Finding Out More About Food Allergies

Our immune system is designed to protect our body from harmful invaders, such as bacteria. Sometimes, however, the system responds to substances normally considered harmless. The substance that provokes the attack is called an allergen; the substances that attack the allergen are called antibodies. A food allergy can provoke such a response as your body releases antibodies to attack specific proteins in food. When this happens, some of the physical reactions include:

• Hives
• Itching
• Swelling of the face, tongue, lips, eyelids, hands, and feet
• Rashes
• Headaches, migraines
• Nausea or vomiting
• Diarrhoea, sometimes bloody
• Sneezing, coughing
• Asthma
• Difficulty in breathing caused by swelling of tissues in the throat
• Loss of consciousness

If you are sensitive to a specific food, you may not have to eat the food to have the reaction. For example, people sensitive to peanuts may break out in hives just from touching a peanut or peanut butter and may suffer a potentially fatal reaction after simply tasting chocolate that has touched factory machinery that previously touched peanuts. People sensitive to seafood-fin fish and shellfish-have been known to develop breathing problems after simply inhaling the vapours or steam produced by cooking the fish.

How an allergic reaction occurs

When you eat a food containing a protein to which you’re sensitive, your immune system releases antibodies that hitch a ride on white blood cells called basophils. The basophils circulate through your entire body, giving the antibodies the chance to hop off and bind to immune system cells called mast cells.

Basophils and mast cells produce, store, and release histamine, a natural body chemical that causes the symptoms-itching, swelling, hives-associated with allergic reactions. Yes, that’s why some allergy pills are called antihistamines. When the antibodies carried by the basophils and mast cells come in contact with food allergens, boom! You have an allergic reaction.

Two kinds of allergic reactions

Your body may react to an allergen in one of two ways-immediately or later on:

• Immediate reactions are more dangerous because they involve a fast swelling of tissue, sometimes within seconds after contact with the offending food.
• Delayed reactions, which may occur as long as 24 to 48 hours after you’ve been exposed to the offending food, are usually much milder, perhaps a slight cough or nasal congestion caused by swollen tissues.

Foods Most Likely to Cause Allergic Reactions

Here’s something to chew on: More than 90 percent of all allergic reactions to foods are caused by just eight foods:

• Milk
• Eggs
• Peanuts
• Tree nuts
• Soybean-based foods
• Wheat
• Fish

Coping with Food Allergies

After you know that you’re allergic to a food, the best way to avoid an allergic reaction is to avoid the food. Unfortunately, that task may be harder than it sounds because the offending ingredient may be hidden-peanuts in the chili or caviar (“fish eggs”) in the dip.

Sometimes the “hidden” ingredient is hidden in plain sight on a food label that uses chemical code names for allergens. If you’re someone with a potentially life-threatening allergy to food (or another allergen, such as wasp venom), your nutritionist may suggest that you carry a syringe pre-filled with epinephrine, a drug that counteracts the reactions.