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October 16, 2012 at 10:11 PMComments: 1 Faves: 0

Food Allergy vs. Intolerance: What's the Difference?

By Jeffrey VanWingen M.D. More Blogs by This Author

Food is a double-edged sword. We are nourished by food. Without it we cannot survive, and it entertains us with different tastes and presentations. Conversely, it causes obesity which can lead to diabetes, heart disease, and stroke - all common causes of death. Food can also be harmful in more immediate ways, such as with allergy and intolerance. 
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However, though often lumped together, these two body reactions to food are distinct. This blog will highlight the difference between food allergy and intolerance.

Food Allergy

What it is: Allergy is an abnormal immune reaction to a substance that comes into contact with the body. This substance may be virtually anything - pollen, a medication, a food, etc, but regardless of the cause, in general, allergic reactions worsen with each subsequent exposure to it. The most severe form of allergy is called "anaphlaxis,"  which can quickly lead to shock and death. Food is a common cause of anaphlaxis, and it's incredible just how little consumption of an allergenic food to spur the body into the anaphlaxis process and how quickly this can occur.
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Symptoms: In the case of food allergy, the symptoms of tingling and swelling often occur within seconds of food's contact with the mouth - fortunately, this gives us time to spit it out and rinse our mouth. Still, the situation is precarious with even this level exposure and often leads to throat swelling, sweating, hives, and shock. (Note: Cramping and diarrhea can be milder symptoms of allergy. But, these isolated symptoms are more likely found in a food intolerance.)
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Treatment: Treatment for this allergy involves an antihistamine like Benadryl and an epinephrine injection like EpiPen. However, emergency medical attention and monitoring should be sought, because the symptoms can return after a couple hours when the epinephrine effect wanes. The presence of hives after eating should prompt allergy testing to determine if there is a food allergy. Remember: allergy worsens with further exposure and the next time could be anaphlaxis!
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Causes: The most common food allergies are nuts and shellfish. Less common allergies are milk, soy, and egg. Then again, any substance can stimulate an immune response in the body. 
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Living with Food Allergies: As a doctor, this is one of the deadliest issues I deal with. Therefore, the severity of anaphlaxis, combined with the common presence of the foods that can cause it, is particularly frightening to me.
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Severe allergy patients need to find balance between living their lives and knowing that a deadly substance may be hidden in one of their favorite foods. This could be a nut camouflaged by the crust of a dessert or a piece of shrimp that may have been inadvertently put into a stir-fry. The situation is even more worrisome for parents of small children with a severe allergy.  Knowing that if your child takes a bite of someone else's peanut butter sandwich it may be their last can, and even should, create a hypervigillant state.
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Fortunately, schools and daycares now understand the seriousness of severe food allergy and have enacted measures such as staff training and allergy-free lunch tables.   

Food Intolerance

What it is: Our bodies must produce an amazing chemistry to digest food on the microscopic level. We have an array of special enzymes to emulsify and break down the various proteins, fats, and sugars that make up foods. Occasionally, though, there is a mismatch between the food we take in and our body's ability to digest it. This happens with a particular defect in the process of digestion or metabolism that causes things to go awry.
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Carbohydrates, or sugars, are one of the fundamental forms of nutrition we use. The use of carbohydrates in our body is a lot like an economy.The currency that can be used in our body is glucose, the most basic carbohydrate. However, entering into the borders of our body are other currencies (carbohydrates) that need to be converted in order to be used.  Examples of the other "currencies" include lactose (milk sugar), fructose (fruit sugar), and starch (complex chains of glucose).
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Normally, enzymes are used to convert these sugars into glucose via chemical reactions without any difficulty. However, if the body is lacking in these enzymes, the sugar cannot be used and continues on through the gut without getting absorbed. This creates an unfriendly environment for the bowels, which leads to a "rapid transport situation" aka: cramping and diarrhea. 
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Symptoms: Food intolerance causes cramping, bloating, and subsequent diarrhea.
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Lactose-Type Carbohydrate Intolerance: The deficiency of the enzyme lactase leads to an intolerance of dairy products. People can be born with this condition or acquire it along the way.  The problem occurs on a spectrum with a wide range of presentations from mild to severe depending on the amount of enzyme produced by the body. Lactose intolerant people do have a choice to avoid or supplement. The enzyme can be taken in a pill form (Lactaid) which allows for digestion of milk products. In short, ice cream may equal diarrhea, but ice cream plus Lactaid equals normal digestion.
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Fructose-Type Carbohydrate Intolerance: This is a less common and less appreciated problem. This intolerance also exists due to the deficiency of the enzyme used to convert fruit sugar to glucose. The condition can be hereditary or acquired and can also exist on a spectrum. While it is obvious that fruits cause problems, the other culprit can be found in high fructose corn syrup which is a common component in processed foods. While not a perfect test, a hydrogen breath analysis can be used to help diagnose fructose intolerance. Treatment involves avoidance of dietary fructose.
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Alcohol-Type Carbohydrate Intolerance: Physiologically speaking, it is true that some people cannot hold their liquor. An enzyme called "alcohol dehydrogenase" is key in metabolizing alcohol and is present in different levels among people. Asians, women, and the elderly have been known to have naturally lower levels of alcohol dehydrogenase. However, this enzyme can increase with frequent, consistent consumption of alcohol. This is why frequent drinkers require more alcohol to become intoxicated. Occasionally, people posses a scant amount of this enzyme and have a real problem with alcohol. A single drink can cause flushing and intoxication.
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Other Types of Food Intolerance: The different intolerance syndromes are too many to mention in this blog. Others include food coloring, food preservatives, and sulfites. Celiac sprue (gluten sensitivity) is complicated when considering whether it is a sensitivity or an allergy. It will be covered alone in a forthcoming blog.

In Conclusion...

Food allergy and food sensitivity are quite different. While both involve food causing an adverse reaction in our bodies, a food allergy can be deadly. Both can also leave a person bewildered, necessitating a close analysis of foods entering the body. This leads to a different relationship with food, the nutritional fuel which most of us without such problems enjoy and take for granted.

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1 Comment

  • Great topic to explain as you are absolutely right. Many people claim they have food allergies, when in actuality it is a sensitivity or intolerance. BIG difference.

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