Food allergies have been on the rise for the past several decades. The Centers for Disease Control and Prevention reports that the prevalence of food allergies in children increased by 50% between 1997 and 2011. It is now estimated that approximately 1 in 13 children have a food allergy. 

If you think you have a food sensitivity, identifying which foods are causing your symptoms can be tricky. 

This has some people turning to online food sensitivity testing to determine if they are a victim of a food allergy. But is this the best route to take and how accurate are these tests? 

Is it a food sensitivity, or intolerance?

"First, it's important to note that not everyone will experience a full-blown food allergy, also called a food sensitivity," says Sara May, MD, Nebraska Medicine allergy and immunology specialist. "And some people experience food intolerances, which is different than a food sensitivity." 

Food allergies or sensitivities are caused by the immune system and typically involve immunoglobulin E (IgE) antibodies, explains Dr. May. When this happens, the immune system incorrectly identifies a food as a danger and produces an IgE antibody. The next time you are exposed to this food, the immune system will react leading to symptoms. These symptoms occur each time you are exposed to the food. Exposure usually requires ingestion. 

What a food sensitivity reaction looks like

Most people will experience symptoms within 30 minutes of eating a food they are sensitive to. 

Food allergy symptoms typically include: 

• Rashes such as hives, swelling of the skin, itching and flushing
• A drop in blood pressure
• Problems breathing
• Abdominal pain or discomfort

This type of reaction is known as anaphylaxis and can be life-threatening. 

What a food intolerance reaction looks like

Unlike food allergies (sensitivities), food intolerances generally are less severe, are not caused by the immune system, but may involve abdominal symptoms similar to food sensitivities, says Dr. May. 

A food intolerance may be due to a digestive enzyme deficiency or poor absorption of certain carbohydrates. With food intolerances, it is more common to experience gastrointestinal problems such as bloating, diarrhea, abdominal cramping, or constipation that may occur hours or even days after eating certain foods. 

The most common food allergies include milk, eggs, soy, wheat, peanuts, tree nuts, fish and shellfish, but you can develop a food allergy or intolerance to almost any type of food. 

Will an at-home food sensitivity test help determine what's causing your symptoms?

In general, Dr. May advises that you steer away from home test kits.

"There are a variety of home food sensitivity and intolerance tests out there, many of which often provide inaccurate results," Dr. May says. "To effectively determine a food allergy, you need to perform the correct type of testing in combination with a medical history evaluation." Many home tests use a food-specific immunoglobulin G (IgG) blood test that measures antibodies to 87 commonly consumed foods. The problem, says Dr. May, is that IgG antibodies actually demonstrate tolerance to food, not intolerance to food. These are not the allergic antibodies. 

"As a result, you may end up with test data that shows a high IgG for many types of foods," she says. "However, there is no research that shows that IgG positivity correlates to intolerance. Due to tests like these, I often have people come to my office with very restricted diets based on their test results and continue to suffer from abdominal symptoms."

More accurate tests to ask your doctor about

Breath test

The best test for food intolerances caused by reduced enzymes is a breath test. These are effective when performed at your doctor's office. 

Diagnosing an intolerance to lactose, found in dairy products, is typically done with a breath test in your doctor's office. This involves measuring the amount of hydrogen gas in your breath before and after you drink a liquid containing lactose. 

You can also try lactose-free dairy products or add lactase before eating dairy and see if you feel better, says Dr. May.

IgE blood test

The allergen-specific immunoglobulin E (IgE) blood test is the type used in doctor's offices to identify food allergies. Similarly, food allergy skin testing is done by an allergist and is the most sensitive way to identify food allergies. Both are more accurate at identifying food allergies than other food intolerance tests. Even with increased accuracy, testing needs to be followed by a medical history evaluation for accurate health recommendations to improve symptoms safely. 

Other food allergy testing

If you experience adverse symptoms when eating foods with gluten, you should discuss symptoms with your doctor. A serum test and endoscopy are needed to diagnose whether you have celiac disease, an autoimmune disease triggered by eating gluten that can be serious and cause the development of a systemic disease. This is a different type of reaction than a food allergy or food intolerance.

When to ask for help with allergies

If you suspect you have a food intolerance or sensitivity, Dr. May suggests that you start with keeping a food symptom journal for a few weeks to document exactly what you are eating and when, as well as the start time and type of any adverse symptoms. 

If you aren't able to figure out which food is causing the problem by journaling, and a food sensitivity is still suspected, make an appointment with your primary care doctor or allergist to follow up with additional testing to identify the specific food triggers.

Always seek immediate medical assistance if you should experience a severe allergic reaction to food.