Our consumption of food nearly triples during the holiday season. With all of the scrumptious variety of foods and gourmet treats we're presented with during the holidays, a food allergy can easily present as one of the holiday's hidden dangers.

A food allergy is an adverse reaction to food that is triggered by the immune system. The body's defense mechanisms "sees" the food that you eat as a foreign intruder and tries to attack it. Many factors affect the degree, timing and the location of an allergic reaction. So what might happen?

If someone is allergic to a particular food, for example, they may first experience itching in the mouth as they start to eat the food. After the food is digested in the stomach, abdominal symptoms such as vomiting, diarrhea, or pain may start. As the allergens reach the skin, they can induce hives, or when they reach the lungs, they may cause difficulty breathing or wheezing.

When the food enters and travels through the bloodstream, there can be a drop in blood pressure leading to anaphylactic shock. These symptoms can appear within a few minutes or as long as a few hours after the food is consumed.

Luckily only one percent of adults and three percent of children have a true food allergy. Generally, people who have food allergies come from families in which allergies such as hay fever, asthma, or hives are common. In adults, the most common foods to cause allergies include: shellfish such as shrimp, crayfish, lobster, and crab; peanuts; fish; and eggs. Adults usually do not lose their allergies.

In children, the most common food allergens are eggs, milk, and peanuts. Children can outgrow food allergies. They are more likely to outgrow allergies to milk or soy rather than allergies to peanuts, fish, or shrimp. The foods that adults or children react to are those foods they eat most often. In Japan, for example, rice allergy is more frequent. In Scandinavia, codfish allergy is more common.

If someone has an allergy to shrimp, they might also have an allergy to other shellfish such as crab, lobster, and crayfish. This is called cross-reactivity. Another interesting example of cross-reactivity occurs in people who are highly sensitive to ragweed. These people sometimes find that when they try to eat melons, particularly cantaloupe, they have itching in their mouth and they simply cannot eat the melon.

Is it a food allergy or food intolerance?

The difficult part is figuring out if you have a food allergy or a food intolerance. The symptoms of food intolerance, like lactose, can easily be mistaken for those of a food allergy. In food intolerance the body is not able to digest a certain food, and it does not involve the immune system. Take for example, lactose intolerance.

Lactase is an enzyme in the lining of the gut, that breaks down lactose, which is found in milk. If a person does not have enough lactase, the body cannot digest most milk products. Instead, the lactose is used by bacteria, gas is formed, and the person experiences bloating, abdominal pain, and sometimes diarrhea. There are simple tests that your doctor can use to determine if you are lactose intolerance. Unlike allergies, food intolerances generally worsen with age.

How is a food allergy diagnosed?

To diagnose food allergy the doctor will first take a detailed diet history. Sometimes a diagnosis cannot be made solely on the basis of the history. In that case, the doctor may ask the patient to keep a record of each meal and whether any symptoms occurred afterwards.

The third step, if needed, the patient eliminates the food suspected of causing the allergy from the diet. If the patient removes the food and the symptoms go away, the doctor can almost always make a diagnosis. If the patient then eats the food (under the doctor's direction) and the symptoms come back, then the diagnosis is confirmed.

If the symptoms are still unexplained the doctor will then use tests that can more precisely measure an allergic response to food. One of these is a scratch skin test, during which a dilute extract of the food is placed on the skin of the forearm or back. This portion of the skin is then scratched with a needle and observed for swelling or redness that would indicate a local allergic reaction.

A doctor diagnoses a food allergy only when a patient has a positive skin test to a specific allergen and the history of these reactions suggests an allergy to the same food. For people not able to undergo skin testing there are two blood tests available: the RAST and ELISA, which measure the presence of anti-body directed against a specific food in the blood of patients. These tests may cost more than skin tests, and results are not available immediately.

How is a food allergy treated?

Treatment for a food allergy is to avoid the offending food, which is easier said than done. Once a person knows which food causes an allergic reaction, the food must be completely removed from the diet. This involves reading food labels carefully before eating foods.

Total avoidance is difficult since many foods such as peanuts, eggs, and milk, are also often hidden as ingredients in casseroles or desserts, and appear in foods one normally would not associate them with. Peanuts, for example, are often used as a protein source and eggs are used in some salad dressings.

Your Thanksgiving Dinner: Does It Present a Food Allergy Danger?

When you are out for dinner or at a holiday party, you won't always be able to read food labels. So if you have a food allergy or suspect that you might, be sure to ask your host what the ingredients are.

For example, many Thanksgiving turkeys are stuffed with foods such as oysters or walnuts; mashed potatoes may contain milk or other dairy products that could cause a food allergy or food intolerance; and pumpkin pie is commonly made with eggs.

Anyone who has a food allergy should wear medical alert bracelet stating to which foods they are allergic. Anyone who has had an anaphylactic reaction they should carry an allergy kit, which contains a syringe of epinephrine, and know how to self-administer it if they think an allergic reaction is developing.

Anti-histamines are included with the allergy kit. Taking the anti-histamine will relieve itchy skin and hives. These medications are taken after people have accidentally eaten a food to which they are allergic but are not effective in preventing an allergic reaction when taken prior to eating the food. No medication in any form can be taken before eating a certain food that will reliably prevent an allergic reaction to that food.

With any significant allergic reaction you should seek medical help by calling 911 and than be transported to an emergency department. Anaphylactic reactions can be deceiving, they can begin with mild symptoms such as a tingling in the mouth and throat or gastrointestinal discomfort and rapidly progress to shock.