Allergy vs Intolerance – How Can You Tell The Difference?


Many people use the word “allergy” to mean anything from a true allergy to a simple intolerance.  It can be very confusing. Hopefully this article will help shed some light on the issue by pointing out the main differences between the two..


Allergies versus intolerance

So you may ask, what exactly is an allergy?  First off, allergies usually come on very suddenly.  A small exposure triggers the body’s response and it happens every time you are exposed to the item.  An allergy trigger can be something in your environment, like grass or mold, or a medication or a food.  You really cannot be allergic to another person, but you could be allergic to something on them like their perfume or cologne.

Mild allergies start with our bodies setting off a histamine release.  We will see hives or a rash form, or start to sneeze and get watery eyes.  Almost always something itches—eyes, nose, skin.  Our body’s immune system gets involved further and makes antibodies against the intruder as well, so we won’t forget it when exposed again.

When allergies are bad enough they can be life threatening.  Anaphylaxis is the worst form of an allergic reaction.  This risk is a major difference between allergy vs intolerance.  It involves difficulty breathing and a huge drop in blood pressure.  Immediate medical care is absolutely necessary.

An intolerance, on the other hand, will come on more gradually.  You may need to have quite a bit of exposure before you have any problems so you either need to be exposed to a large amount of the item or have frequent exposure.  And lastly, intolerance, no matter how uncomfortable, is not life-threatening.


Food reactions

Eliciting which you have, an allergy vs intolerance, or sensitivity to a food, can be one of the trickier decisions. This is because they can share symptoms.  Nausea, stomach pain, diarrhea, and vomiting can occur with allergies or as food sensitivity symptoms.  When a food irritates your stomach, or you can’t really digest it properly, that is an intolerance.  You may develop gas, cramps, bloating or indigestion (heartburn).  You could also feel irritable or nervous or develop a headache.

With a true allergy to a food your immune system mistakes protein in the food as an invader and attacks it.  This leads to your whole body reacting.  You may develop a rash or hives, or get an itchy mouth or nose.  Your face and mouth could swell.  If the allergy is bad enough you could develop anaphylaxis.

The most common food allergy is to peanuts (more on this here). Other common trigger foods include walnuts, pecans and almonds, fish and shellfish, milk, eggs, soy, and wheat.  When you have an allergy to a food you need to avoid it completely.  You may even need to carry an EpiPen in case of a reaction.

The most common food intolerance is to lactose in milk and other dairy products.  Lactose is a sugar found in dairy products and many people lose the enzyme which breaks it down as they age.  When you have an intolerance to a food you can still eat it, but need to be ready for the discomforts it causes.  Most people will tend to stay away from eating foods that create distress.

Food poisoning is not an allergy or intolerance.  Toxins from bacteria that grow in the spoiled food can cause severe digestive system symptoms, but once the bad food is out of your system and your body recovers you will not react to that food again as long as it is not spoiled.


What about gluten?

breads on plate

Celiac disease is an autoimmune disease.  It is also called gluten sensitive enteropathy and it involves the immune system.  The small intestine becomes inflamed and damaged when gluten, a protein found in wheat, rye and barley, is eaten.  As the body responds to the gluten it attacks its own intestinal tissue.  The damage leads to mal-absorption of nutrients and multiple medical issues.

Gluten sensitivity or intolerance is different from celiac disease in that the body reacts with a different immune response that does not attack and damage the lining of the small intestine.  The body does create an inflammatory response but it could involve the entire bowel, joints, skin, or muscles.  Fatigue, headaches, and depression can also occur.  While not a true gluten allergy, the person will feel best if they remove it from their diet.

Luckily, gluten rarely if ever causes life-threatening symptoms, but it can make a person very sick.


It can be difficult sometimes to determine if you have an intolerance vs a true allergy.  If that is the case, seek care from your doctor or a specialist.  Via a series of tests, looking at your history and other factors, they can help you determine which problem you have.

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