Understanding the Distinctions: Food Allergy, Intolerance, or Sensitivity

Chances are, either you or someone you know has experienced unpleasant symptoms following a meal. From sneezing and rashes to joint pain and bloating, these symptoms can range from annoying to potentially life-threatening. While many people may attribute these reactions to food allergies, there are other possibilities to consider, such as food intolerances, celiac disease, or food sensitivities. In this article, we will explore these different conditions, their causes, and how they can be managed for a better quality of life.

Food Intolerances

Food intolerances primarily involve the body's inability to process or digest certain foods. One of the most common food intolerances is lactose intolerance. As we age, our ability to digest dairy decreases because our intestines produce less lactase, the enzyme responsible for processing lactose found in milk and dairy products. This buildup of lactose in the digestive tract can lead to symptoms like stomach bloating, inflammation, and diarrhea. Surprisingly, only about 35% of people worldwide can digest lactose beyond the age of seven or eight. While lactose intolerance is not a serious disease, it can be uncomfortable. Avoiding dairy products or using over-the-counter lactase enzyme supplements can help manage the symptoms.

Food Allergies

Food allergies, on the other hand, involve a more severe immune response to certain foods, posing a potentially life-threatening risk. These allergic reactions occur when the body's immune system overreacts to a seemingly harmless substance, which in this case is food. An example of a severe food allergy is difficulty breathing and low blood pressure that can occur after exposure to peanuts or seafood. Food allergies can develop at any age and should be taken seriously, especially if symptoms are severe. Allergy testing, closely reading ingredient labels, and carrying epinephrine shots in case of accidental ingestion are important steps in managing food allergies and preventing life-threatening situations.

Celiac Disease

Celiac disease is an autoimmune condition that affects approximately 1% of the Western population. In individuals with celiac disease, the ingestion of gluten triggers an inflammatory reaction in the body, causing significant discomfort. While celiac disease is not a true allergy and does not cause an immediate life-threatening problem, prolonged exposure to gluten can lead to symptoms such as diarrhea, weight loss, and malnutrition. The only effective solution is to avoid gluten, which is found in grains like wheat, rye, barley, semolina, bulgur, and farina. People with celiac disease must also be cautious about cross-contamination, where gluten-free foods come into contact with gluten-containing foods.

Food Sensitivities

Food sensitivities are different from food intolerances, allergies, or celiac disease. After consuming certain foods, a significant portion of the population experiences symptoms that are unrelated to these conditions. These symptoms, known as food sensitivities, can disrupt daily life and manifest in various ways such as joint pain, stomach pain, fatigue, rashes, and brain fog. While the exact mechanisms behind food sensitivities are still debated, it appears that specific foods can trigger an immune reaction, leading to these diverse symptoms. Although not life-threatening, food sensitivities can significantly impact one's well-being. The most effective way to identify food sensitivities is through a process of careful observation and experimentation. Eliminating suspected trigger foods from the diet for a few weeks and gradually reintroducing them can help pinpoint the culprits. Consulting with a physician or nutritionist is valuable in undertaking an elimination diet and gaining guidance to avoid potential pitfalls.

Managing Food Reactions

It's important to note that food sensitivities and other reactions can change over time. Our bodies, immune systems, and gut microbiome are constantly evolving, so what may cause discomfort today might be well-tolerated in the future. As such, individuals may consider reintroducing small amounts of previously sensitive foods to assess their current tolerance levels. The bottom line is that while identifying the cause of food reactions can be challenging and time-consuming, it's well worth the effort. Once the problem and triggering foods are known, consulting with a professional, such as a nutritionist or physician, can help guide the development of a safe and individualized diet plan.


Understanding food reactions goes beyond simply labeling them as allergies. By differentiating between food intolerances, allergies, celiac disease, and sensitivities, individuals can better manage their symptoms and improve their overall well-being. While the journey to uncovering the cause may be complex, taking the time to identify trigger foods and seeking expert guidance can lead to the development of a personalized and comprehensive diet for a healthier life.

William H. McDaniel, MD

Dr. Robert H. Shmerling is the former clinical chief of the division of rheumatology at Beth Israel Deaconess Medical Center (BIDMC), and is a current member of the corresponding faculty in medicine at Harvard Medical School.

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