6 Things Every Parent Should Know About Food Allergies

When you were growing up, food allergies and intolerances weren't likely on your parents' radar. But these days, it feels like everyone's talking about them: Is Tommy allergic to peanuts? Can Susie have eggs? 

According to Food Allergy Research and Education (FARE), 5.6 million children have food allergies in the United States, equating to roughly one in every 13 kids—an increase of 50 percent between 1997 and 2011, according to the Centers for Disease Control and Prevention.

Food allergies can also have serious consequences. Not only can they be life-threatening, but FARE reports caring for children with food allergies costs U.S. families nearly $25 billion annually. 

For these reasons, it's important to know the differences between allergies and intolerances, along with the signs, symptoms, and treatments for each. Here are six facts every parent needs to know as they expand their child's diet.

Allergy Fact #1: There's a Difference Between an Allergy and Intolerance

Simply put, allergic reactions happen when your immune system develops an increased sensitivity to a food.

Your body sees the food as a foreign invader, and in response releases chemicals to seek and destroy the offending food, says Purvi Parikh, M.D., pediatric allergist and immunologist at NYU Langone Health.

These chemicals cause the allergic reaction. A severe one can be life-threatening, often requiring an immediate dose of emergency epinephrine via what's commonly known as an EpiPen.

Intolerances are more of a side effect of the food on your digestive system—they have nothing to do with your immune system and, as a result, aren't as dangerous. That said, some people may have extreme sensitivity to certain foods, so exposure to even a tiny amount—a half teaspoon of sugar, if you're sucrose intolerant—can cause symptoms.

Intolerances vary by person. Lactose intolerance, for example, can be relatively mild or quite severe. Some people may be able to consume the food in limited quantities—a splash of cream in your coffee, while others can have an occasional bowl of ice cream.

Allergy Fact #2: Eight Foods Cause 90 Percent of Allergic Reactions

The quick list: milk, eggs, wheat, tree nuts, peanuts, shellfish, fish, and soy. The most common to crop up in children are milk, eggs, peanuts, wheat, soy, and tree nuts, according to Johns Hopkins Medicine.

RELATED: Worried about a milk allergy? Watch for these sneaky ingredients.

But there's growing concern over sesame, as new research has found more than 1 million U.S. children and adults have the allergy and, as the ninth most common allergen, it isn't required to be identified on food labels. (The Food Allergen Labeling and Consumer Protection Act of 2004 requires the top eight to always be listed.)

Those aren't the only foods to be wary of, though. FARE says more than 170 foods have been reported to cause reactions in the United States.

In addition, having one allergy often means others will emerge over time—doctors call it the allergic march. About 40 percent of children with food allergies have more than one. They are also more than twice as likely to have asthma and more than three times as likely to have a respiratory allergy or eczema, FARE adds.

Allergy Fact #3: Some Warning Signs Hide in Plain Sight

About 90 percent of allergic reactions show up on the skin, such as a rash, hives, eczema, itching, or swelling, Dr. Parikh says. Other telltale signs: tingling in the mouth, swelling of the tongue and throat, coughing, wheezing, shortness of breath, diarrhea, vomiting, and loss of consciousness.

The most serious response, of course, is anaphylaxis, which the Mayo Clinic says can occur within seconds or minutes of exposure (click here to find out why)and can cause you to go into shock. If not treated quickly enough with an EpiPen, the situation can become deadly.

Typically, there's a very clear pattern when your child eats an allergy-causing food, Dr. Parikh says, and symptoms usually pop up within 30 minutes to two hours. But the severity of those symptoms may differ if they didn't directly eat the food—limited skin contact or breathing around the ingredient, for example, can still cause a reaction, even if it ends up being less harsh.

Still, FARE notes more than 40 percent of those with food allergies have experienced a severe reaction, so it's always smart to have an EpiPen on hand.

Allergy Fact #4: Reactions Can Ebb and Flow

If you only notice isolated skin symptoms after giving your child a new food, call your doctor and ask for guidance on how best to proceed, Dr. Parikh says.

But if you see skin symptoms in addition to any of the others noted above, Dr. Parikh says it's likely your child is experiencing anaphylaxis, and time is of the essence—use the EpiPen if you have one, call 911, and get to the emergency room ASAP.

Once you've been checked in and treated, experts recommend staying in the emergency room for four to six hours of monitoring. Symptoms can return after initially easing, so stick around until doctors are sure you're in the clear.

Allergy Fact #5: Some Allergies Can Be Prevented

Talk of anaphylaxis can make a parent not want to introduce new foods. But recent research suggests you do the opposite.

"The American Academy of Pediatrics now recommends parents introduce these foods around four to six months of age to prevent the development of food allergies," Parikh says.

After a child is able to keep his or her head upright, test one new food at a time (here are the best foods to start with), serving it in small amounts every two to five days, Dr. Parikh suggests. Be sure to prep the food in a form that's safe for them to eat—oats, for example, should be thinned and pureed with water or breast milk to make them easy to swallow, Dr. Parikh says.

That said, if your kiddo is considered high risk—meaning they have severe eczema or an already-diagnosed egg or milk allergy—hold off on doing any food introductions by yourself.

"In these instances, you should consult with a board-certified allergist or a knowledgeable pediatrician who will give guidance on how and when to safely introduce the other foods, and will tell you if additional testing may be necessary," Parikh says.

Allergy Fact #6: Expect a Lot of Trial and Error

There's no perfect age to start testing your child for food allergies—it's more likely you'll book an appointment with the allergist once they begin showing symptoms of a reaction.

But the testing can even be performed on infants, Dr. Parikh says, and it'll either be a skin or blood test (watch Does a Skin Prick Test Hurt?). If the test results are unclear, your allergist may then do an oral food challenge to see if anything triggers a reaction. 

As for intolerances, unfortunately Dr. Parikh says there isn't yet a reliable, validated test, so trial and error is standard. But ruling out allergies is the strong start to helping your child enjoy new foods while staying safe.

This story has been medically reviewed by Stan Cohen, M.D., a pediatric gastroenterologist at the Children's Center for Digestive Health Care in Atlanta and the director of Nutrition4Kids Medical Advisory Board.