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A Guide to Food Allergies, Food Sensitivities, and Food Intolerances: How are they similar and how are they different?

By Caitlin Beale, MS, RDN+

Is there a link between the food you eat and the way you feel?  If you’ve ever wondered this, you aren’t alone.  People are increasingly aware that even general discomforts like low energy or itchy skin may connect to your diet.  Food sensitivities, food allergies, and food intolerances are all related to what you eat, but the underlying reasons why they happen differ significantly. 


If you think you are reacting poorly to something you are eating, it’s helpful to understand the difference between these three, so you can make the necessary changes to feel better fast.  


What is a food allergy? 


The biggest reason food allergies are different from sensitivities or intolerances is how your immune system responds.  Food allergies occur when antibodies (IgE antibodies) trigger the body to release molecules that drive inflammation and cause accompanying symptoms.i These responses usually happen immediately after exposure to the food. 


Food allergies can be life-threatening for some people because the immune system has flagged a harmless ingredient as a significant danger.ii  The most common food allergies include:iii 

  • Peanuts 

  • Tree nuts 

  • Wheat 

  • Eggs 

  • Shellfish 

  • Fish 

  • Soy 

  • Cow’s milk 


Reactions to food are also significantly on the rise globally.  Research suggests that allergies to foods like peanuts have doubled in the United Kingdom or tripled in the United States, and similar increases were also seen in overall food allergies for children in China iv and India.v 


Cow’s milk and egg are consistently the most prevalent food allergies in children globally. Still, the prevalence of allergies can vary depending on geography and regional food patterns. 5  For example, chickpeas are a top food allergen in India, while buckwheat is an anaphylactic trigger for children in South Korea and Japan, reflecting commonly eaten foods in these countries. 5 


Symptoms of food allergies 


Food allergy symptoms depend on the location of the immune cells involved. They can include skin reactions like hives or rashes, GI discomfort with cramping or diarrhea, or swelling and difficulty breathing.  The most severe reaction is anaphylaxis, a life-threatening response to an 


How are food allergies diagnosed? 


Generally, food allergies are diagnosed by a health care practitioner specializing in allergy and immunology.  Testing can include a blood or skin prick test with appropriate interpretation by the physician.  While some childhood allergies reduce with age, for most people, once diagnosed, that ingredient has to be avoided forever, and even small amounts can cause a response. 1 


What causes food allergies? 


The underlying reasons for food allergies are complex, and scientists believe they are likely related to a combination of genetics and environment.vii  This means that you may be predisposed to develop an allergy if you have a family member with food allergies, but exposures or habits can increase the risk.  Aside from gender and genetics, some of the possible risk factors include: 

  • Low vitamin D statusviii 

  • C-section deliveryix 

  • Age of first food introductionx 


Are food sensitivities the same as food allergies? 


The short answer is no.  Food sensitivities may involve the immune system, but the pathway is different than food allergies.  They also don’t cause anaphylaxis.   


However, just because they aren’t life-threatening doesn’t mean that sensitivities don’t significantly impact your health.  Like allergies, they can activate your white blood cells to release pro-inflammatory mediators that lead to symptoms (but don’t involve IgE antibodies).xi   


Food sensitivities can occur soon after ingesting the ingredient, but you might not have a response for up to 72 hours later.  This is known as delayed hypersensitivity.xii 


Are food sensitivities as common as food allergies? 


Tracking the prevalence of food sensitivities isn’t easy because there isn’t a well-regarded diagnostic tool (as you will learn below).  There are common sensitivities such as non-celiac gluten sensitivity (NCGS), but responses can also happen with chemicals or additives in the food itself, including chemicals like food coloring or sulfites or naturally occurring compounds like caffeine in chocolate. xiii 


What are the symptoms of food sensitivities? 


Because the inflammatory mediators travel throughout your body, they can affect many different body systems.  Symptoms of food sensitivities can range from mild to severe and can include:  

  • GI-related such as nausea, constipation, vomiting, diarrhea, bloating, or crampingxiv 

  • Brain fogxv 

  • Skin conditions and rashesxvi 

  • Migraines or headachesxvii 

  • Body pain and swollen jointsxviii 


How are food sensitivities diagnosed? 


As mentioned, diagnosing food sensitivities can be tricky and is usually based on a process of elimination.  For some time, food sensitivities were not well recognized in the medical field, but because of rising cases such as NCGS, they are increasingly recognized.xix  However, they are still not as well understood as food allergies.xx 


Standard food allergy tests won’t show food sensitivities because they involve completely different parts of the immune system.  While there are several food sensitivity tests available, most are not well validated.xxi 


As a result, food sensitivity tests can act as a starting point, but elimination diets are the accepted gold standard.  And since food sensitivities can be so delayed or symptoms are easily chalked up to other health conditions, working with a healthcare practitioner specializing in food sensitivities can help you narrow down the problematic ingredient. 


What causes food sensitivities? 


The reasons for food sensitivities are not entirely understood, though many experts suggest that a likely cause is related to gut dysbiosis, an imbalance of your commensal gut bacteria.xxii  An unhealthy gut can also damage your intestinal lining.  When the gut lining is compromised, it can allow unwanted food proteins and other molecules into circulation, causing an immune response. 22 


It’s common to have more than one food sensitivity, unlike allergies or intolerances that are often specific to one or two foods.  Sensitivities can also change over time.  Unlike allergies which remain constant (aside from children who grow out of them), addressing the reason you have the sensitivities, such as inflammation from dysbiosis, can improve the sensitivity over time for some people. 


What are food intolerances? 


Sometimes food intolerances are incorrectly labeled food sensitivities, but they aren’t the same.  While symptoms can be similar, intolerances are different because they don’t involve the immune system at all.  Instead, food intolerances occur in the gut due to functional digestive issues that cause difficulty digesting specific foods.xxiii 


What are common food intolerances? 


The most common food intolerance is lactose intolerance.  This happens when you lack the enzyme lactase that breaks down lactose, a sugar found in dairy products.  Globally it’s estimated that 68% of the world’s population has some form of lactose malabsorption.xxiv   


Another common intolerance is related to foods containing FODMAPs.  FODMAPs is an acronym that stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, a group of short-chain carbohydrates. People with FODMAP intolerance have a difficult time digesting these foods.xxv   


What are the symptoms of food intolerances? 


Because intolerances are related to issues digesting specific foods, symptoms of intolerances tend to stay in the GI tract and include:xxvi 

  • Bloating 

  • Constipation 

  • Pain 

  • Diarrhea 

  • Gas 


How are food intolerances diagnosed? 


Generally, food intolerances are also diagnosed by an elimination diet with the suspected food.  For example, with lactose intolerance, simply removing dairy resolves symptoms.  There is a test for lactose intolerance, but many physicians just have their patients remove dairy to avoid a more invasive procedure. 


Graph showing different food allergy symptoms and responses


Support your health by addressing your food-related symptoms 


If you suspect there’s a relationship between what you eat and how you feel, getting to the root cause is vital for feeling like yourself again.  Allergies are the most serious of the three, but food sensitivities or intolerance can still significantly impair your quality of life. 


Once you figure out what food your body is reacting to, it’s essential to avoid that ingredient, no matter the underlying reason.  Even trace amounts can impact sensitive people, so it’s critical to know how to check all your food labels—including your supplements—to ensure you are completely avoiding them.   


Whether a food allergy, food intolerance, or food sensitivity, working with the appropriate healthcare practitioner to guide you through testing and elimination is especially helpful for supporting your long-term health. 



Caitlin Beale, MS, RDN is a registered dietitian and freelance health writer. She has a master's degree in nutrition and over ten years of experience as a registered dietitian. You can learn more about Caitlin Beale, MS, RDN at [optional]  
+The views expressed in this article are those of the authors. They do not reflect the opinions or views of Pure Encapsulations®.