Updated on February 29, 2024.
If your skin breaks into a fiery or itchy rash, your tongue swells, and breathing becomes difficult shortly after eating shrimp, there’s a good chance that you’re allergic to shellfish. Before you tear into another piece, you should speak with your healthcare provider (HCP) about a potential shellfish allergy.
Although not all food allergies present in the same way, true food allergies have similar characteristics: They trigger an immune system response like a rash, trouble breathing, or swelling of the mouth. They tend to cause exaggerated symptoms that can be severe and life-threatening, and appear within a few minutes or hours of eating.
In these cases, the specific allergen is often easy to pinpoint. “If symptoms come on quickly after the food is ingested, it's easy to pick up and diagnose for most people,” says Mark Schecker, MD, and allergy and immunology specialist with Grand Strand Regional Medical Center in Myrtle Beach, South Carolina.
But not all unpleasant reactions to food are allergies. “When you use the term ‘food allergy,’ you're usually referring to something that's very specific,” Schecker says. “And there is a lot of misunderstanding about what food allergies are."
When it’s not an allergy
If your body’s reaction to a specific food isn’t an allergy, what is it? Likely, it’s a food intolerance to a certain food or group of foods, such as wheat, dairy, soy, corn, or fructose. This is sometimes called a food sensitivity.
When you have an intolerance, your body has problems digesting certain foods. This could happen for many different reasons, such as a lack of digestive enzymes, sensitivity to additives, or a reaction to substances in the food.
Unlike an allergy, an intolerance doesn’t typically cause an immune reaction. Instead, food intolerance symptoms tend to involve digestive system issues. These can include:
- Stomach cramps
- Nausea
- Vomiting
- Bloating
- Heartburn
- Diarrhea
Some people experience symptoms unrelated to the digestive tract. Those with a food sensitivity might even have symptoms like a cough, headache, or runny nose. And unlike an allergy, signs of an intolerance are usually less serious and more easily ignored.
The symptoms aren’t the only difference between an allergy and an intolerance. The timing of symptoms differs, as well. “Symptoms that appear after two hours of eating a food are usually not from allergy,” Dr. Schecker says.
Food intolerance symptoms can occur several hours, or even days, after eating. This can make the source of discomfort hard to diagnose. You could be experiencing signs of sensitivity without realizing it.
It should be noted: Wheat intolerance and wheat allergy are different from autoimmune disorders like celiac disease. When you have celiac disease, ingesting gluten—a protein in wheat—can damage the lining of the small intestine. Celiac disease does cause an immune response, but it’s not the same as that of a true allergy.
Symptoms of celiac disease appear between 48 and 72 hours after ingestion, and include abdominal bloating and pain, diarrhea, vomiting, constipation, heartburn, fatigue, headaches, and joint pain.
A difficult diagnosis
Sometimes, food allergies can be diagnosed by symptoms alone. Other times, allergies are easily diagnosed with skin and blood tests.
Food intolerances, on the other hand, are a bit more difficult to pinpoint. “Other sensitivities to foods are much more difficult to diagnose because we don't have diagnostic testing,” Schecker says.
Without a test for food intolerances, HCPs must look to other options, like removing possible triggers from a person’s diet.
“Sometimes, the only way to determine an intolerance is to eliminate certain foods from the diet, and try to gradually reintroduce one at a time,” Schecker says.
A food diary may also be helpful. Logging your daily meals and symptoms over a period of time may help narrow down some common triggers.
Finding a solution
After your HCP has successfully diagnosed your sensitivity, you will likely work together to determine the best way to control or avoid food intolerance symptoms.
Treating food intolerance focuses on avoiding or limiting intake of the troublesome food. Small amounts of the food may not cause a reaction, in which case eliminating the food entirely may not be necessary.
In instances where enzymes, responsible for breaking down certain foods, are deficient, some over-the-counter medications can be taken before a meal. Lactase enzymes, for example, may help reduce the effects of a dairy intolerance.
