Are we more worried about food allergies than we should be?

Under normal conditions, your immune system is on guard against foreign invaders, known as antigens. These can be viruses, bacteria or any harmful substance. When an invader is found, the immune system releases protective proteins -- known as antibodies or immunoglobulins -- to attach to other immune cells called mast cells. When the offensive object encounters this mast cell/immunoglobulin hybrid, the antigen attaches to it. The mast cell then releases histamines and other chemicals to destroy the antigen. A food allergy -- or any allergy -- occurs when something triggers your immune system to have an abnormal response against a harmless substance that your body mistakes for a harmful agent.

True antigens prompt the response of one of four different types of immunoglobulin: G, M, A or D. Allergic reactions, however, prompt the production of a unique immunoglobulin, known as E, or IgE (immunoglobulin E). It's the presence of IgE that identifies a reaction as an allergic reaction. The half-life of IgE is 2.3 days, so if you have recurring symptoms over a period of days or weeks, it's due to continued exposure and continued manufacture of IgE [source: Ishizaka].

Common allergic symptoms include:

Peanuts are the most likely food allergen to cause a life-threatening situation in the form of an anaphylactic reaction, which is basically a multisystemic meltdown that can put a person into a state of shock. For every five deaths related to a food allergy, four are caused by peanuts [source: Schwartz].

Food allergies aren't the only things that cause anaphylaxis. It can be triggered by penicillin, pollen and stings from insects such as bees or hornets. One treatment of anaphylaxis is a dose of epinephrine that helps end the state of shock by boosting blood pressure and opening up the airways in the lungs. Epinephrine can be administered (or self-administered) via injection into the thigh with a small penlike device that many food-allergic children and adults carry with them at all times.

Anaphylaxis can cause severe reactions to many parts of the body at once, including the throat, lungs and skin. However, anaphylactic reactions aren't always so severe, sometimes causing nothing more than a skin rash or mild asthma.

But it's possible to have allergylike symptoms and feelings after eating without any need to reach for the epinephrine pen. We'll learn how and why in the next section.

Sometimes, we have negative experiences with food and declare them "allergic reactions" when really these are instances of food intolerance. A food intolerance is also an abnormal reaction to food, but it can take many forms and never involves the release of IgE, which occurs only during allergic reactions.

Food allergies aren't the same as food intolerances. For instance, lactose intolerance isn't an allergy. Having a toxic reaction -- as you may if you eat tainted shellfish -- isn't an allergic reaction either, and neither is food poisoning.

Food intolerance occurs far more often than food allergy, but shares many of the same symptoms as (such as nausea or stomach pain). The key difference is that food intolerance is a response of the digestive system, while food allergy derives from the function of the immune system.

A negative reaction to milk could either be lactose intolerance or milk allergy. In some cases, milk allergy, which is one of the most common food allergies in children, can resolve itself entirely as children age. Lactose intolerance, which is more commonly developed in adulthood, is a lifelong condition. While other allergies -- such as wheat allergy -- may also diminish with time, some can affect you throughout your entire life.

An increased alarm and awareness of food allergies likely brings with it an increased likelihood of mistakenly declaring a negative reaction to food to be an allergy.

You probably don't know too many people who are allergic to apples or carrots (depending on what type of crowd you run with), but more adults are allergic to fruits and veggies than they are to peanuts. Most of us tend to think of peanuts as the most common allergy because of the frequency with which we hear about it in the media. Peanuts earned their star status for their potential to cause deadly allergic reactions, not for the frequency of which that actually happens.

That's not to say it never happens, however: While "only" 0.6 percent of the U.S. population is allergic to peanuts, that still represents more than 1.8 million people of all ages who are at some degree of known risk of experiencing a more dangerous reaction than occurs with other types of food allergies [source: Stoppler].

Next: Seriously, should we panic about food allergies?

In 2007, around 3 million children under the age of 18 (of 73 million U.S. children, about 1-in-25, or almost 4 percent) were reported to have a food-related allergy [source: National Center for Health Statistics]. Interestingly, in 2006, there were fewer than 10,000 total hospital discharges of children for food allergies [source: NCHS Press Room].

What's the reason for the disparity in the large number of children who are reported to have food allergies and the relatively small number who are hospitalized?

Fortunately, not all children who have food allergies will require hospitalization. But another reason for the disparity could be that much of the available data is collected through verbal interviews -- simply asking a random sampling of parents if their children, yes or no, have food allergies.

The number of children with clinically proven food allergies is somewhere around 3 percent, or 2.1 million [source: Stoppler]. But according to parents' own yes-or-no responses, around 3 million kids have allergies. That's a difference of nearly 1 million children.

So what accounts for that difference? There are certainly some children who have had food allergy reactions whose parents haven't followed up those episodes with a doctor's visit for diagnosis. But likely there is also a sizable number of parents who have simply reported their children to be food-allergic when in fact their children have some form of food intolerance. It's an easy mistake to make, since food intolerance can have such similar symptoms as food allergies.

Food allergies are very dangerous, but somewhat less common than most of us tend to think. Of course, that's no solace to those who are food allergic, and widespread awareness is certainly a good thing when it comes to our individual and collective abilities to identify and respond to an allergic reaction. You will want to follow your pediatrician's advice when it comes to your child's diet, but your child isn't so likely to develop a food allergy that you should stay up at night breaking out in hives worrying about it.

See the next page for lots more information on food allergies.