Food Allergies


Reactions to food are common. These reactions range from mild to severe, and may result from your body's negative response to certain foods or from a true food allergy.

The job of immune system cells is to find foreign substances such as viruses and bacteria and get rid of them. Normally, this response protects us from dangerous diseases. People with food allergies have super-sensitive immune systems that react to harmless substances found in food and drink. These substances are called allergens. When people have an allergy, there are antibodies to the allergens in their blood and throughout their body. When that person eats a food to which they are allergic, the food allergens react to antibodies on cells releasing chemicals.

Who Gets a Food Allergy?

From 3 percent to 8 percent of children have reactions to some foods. Only 1 percent to 2 percent have true food allergies. Some children seem to grow out of their sensitivity to certain foods, often by age 4. Allergies to peanuts, tree nuts and shellfish usually do not go away, though.

From 1 percent to 2 percent of adults have true food allergies. But people of any age can have sudden allergic reactions to a food that had previously not been a problem for them.

If you have an allergy, a reaction is triggered within minutes to two hours after you consume the allergen. How soon and how severe the reaction is depends on how sensitive you are to the food, the amount of the food consumed, other food consumed, the manner in which it is prepared (i.e., cooked or uncooked, seasoned or unseasoned), and any other medical problems you have.

Severe, life-threatening reactions are more common with allergies to peanuts, tree nuts, shellfish, fish and eggs. These life-threatening reactions are more common in people who also have asthma.

What are the Symptoms?

Reactions can affect different body systems:

The digestive tract, which first comes into contact with food. Some symptoms, such as swelling and itching of the lips, the lining of the mouth as well as throat tightness and hoarseness may occur quickly. When the food enters the stomach and then the intestines, nausea, cramping, pain, vomiting and diarrhea may occur.

Body systems, such as the skin, lungs and blood vessels that are affected after the food leaves the digestive tract. These reactions can occur in minutes or within two hours. Often, hives and swelling of the skin occur. Anaphylaxis, the most dangerous and life-threatening result of a food allergy, usually occurs within minutes after consuming the food. When this happens, blood vessels widen so much that blood pressure falls. Symptoms include wheezing, difficulty breathing, throat tightness, nausea, rapid pulse, flushing, faintness, itching of the palms and sole of the feet and even passing out. Without speedy treatment, this intense allergic reaction can cause death. The first severe reaction to a food may be unexpected. Sometimes the patient may at first have minor symptoms such as stomach cramping or hives

How is a Food Allergy Diagnosed?

If your doctor suspects you may have a food allergy, the first step is to take a detailed medical history and physical eAxam. Other tests are used to confirm that you are allergic to certain foods. Some tests use extracts of the suspected foods:

    • Allergy skin prick test- The skin test involves scratching or pricking your skin with one or more extracts. Allergy prick test to food is more sensitive and specific compared to blood alllergy test.
    • Ig E Antibodies to FOOD ALLERGENS by IMMUNOCAP ELISA test is done in a laboratory. It is used to test a sample of blood for antibody to a specific food. While more costly and less sensitive than skin testing, it is particularly useful when eczema and other skin conditions make skin testing difficult.
    • Another test is the oral food challenge. This test provides the most convincing results. It is required if the relationship between the eating a specific food and symptoms is still unclear after skin tests. Your doctor will explain that all oral challenges -- giving patients the suspected foods -- carry a risk of causing an allergic reaction. They should be done with a specialist physician present and in a setting where allergic reactions can be treated promptly. If the diagnosis is still unclear, you may be put on an elimination diet. The first step is to follow the usual diet for 10 to 14 days. You keep a record of what and how much you eat, when a reaction occurred, and what the reaction was. The foods suspected of causing the reaction are then removed from your diet. Make sure that the foods are not in other foods you eat. For example, egg or milk may be in mayonnaise or salad dressings. Elimination diet should only be used for a limited period of time such as 10-14 days.

Are There Other Concerns in Diagnosing a Food Allergy?

Several factors make diagnosis difficult. The reaction may depend on the amount of food consumed, the presence of other foods that can slow digestion, and medications such as antihistamines that may hide reactions.The proteins -- the antigens within the food or drink that cause the allergy -- may be altered by cooking or processing in some way. The antigens may be in only part of the food, such as the skin of an apple. Some are present only at a particular stage of ripeness.

Reaction apparently due to a food or food additive may in reality be due to another food that was accidentally added to the mixture during preparation. Toxins and food poisoning can cause symptoms that can be confused with food allergy. Some foods upset the stomach and resemble food allergy. Examples are prunes, soybeans and onions. Some medical conditions such as hiatal hernia, ulcers and diverticulosis are associated with acute symptoms after eating. Some people can't digest lactose, because they don't produce enough lactase, and may have symptoms after drinking milk. The reactions may be confused with food allergy.

What Can Be Done to Avoid Developing Food Allergies?

To prevent or modify the development of food allergy, identify early in life people who are most at risk:

Those with a family history of allergy

Allergic reactions to cow's milk or soy formula can appear within days or months after birth. There is evidence that infants who are breast-fed exclusively during their first six to 12 months of life develop fewer allergies by age one or two than infants fed with formula. The American Academy of Pediatrics (AAP) recommends exclusive breast-feeding as ideal nutrition for about the first six months of life.

What are Some Tips to Follow to Prevent an Allergic Reaction?

Do not consume foods that cause a reaction. People with a severe allergy can go into anaphylactic shock from trace amounts of the food to which they are allergic. Touching foods cause some people to have a severe reaction.

Read the ingredients lists on food labels to make sure allergy-causing foods are not mixed in. Read the list even if you have had the product before. Ingredients may change.

When eating out, always ask restaurant staff about ingredients in food and how it was prepared. Cooking oils can have allergens. Peanut oil is often used in cooking, particularly in Thai cuisine.

For infants, elemental formulas or formulas with altered protein should prevent food reactions. Discuss the various formula options with your doctor. Do not assume products labeled "hypoallergenic" will not cause a reaction.

What Can Do If I Have a Reaction?

If you have a severe reaction, take medication and seek medical care promptly. Injectable epinephrine, should always be at hand for treating anaphylactic shock. Get medical care promptly after using epinephrine, even if you feel better. Symptoms may reoccur in a few hours. Antihistamines and steroids also may be taken to lessen symptoms. Prompt treatment often can limit the severity of the reaction.