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Diarrhea, itching and rashes can all be signs of a food allergy. They could also be symptoms of some cancers, including colorectal cancer, pancreatic cancer, and leukemia. 

So, how do you know if they¡¯re due to food allergies or something else? And, when should you see a doctor about them? 

We checked in with senior clinical dietitian Beverly Rodgers for advice.? 

What¡¯s the difference between a food allergy and a food intolerance?

There are actually three categories to be aware of here:  

• Food allergy 
• Food intolerance 
• Autoimmune diseases that affect the gut 

A food allergy can cause gastrointestinal issues, such as gas, bloating and diarrhea. But a true allergy will also involve some degree of anaphylactic response, such as hives, itching or your airway closing up. Some people are so allergic to things like peanuts or shellfish that ingesting even the tiniest bit of them can be life-threatening. That¡¯s why they carry around epinephrine injectors.   

Food intolerances, on the other hand, are usually not dangerous ¡ª just very uncomfortable. One good example is lactose intolerance. That¡¯s when you can¡¯t digest milk or other dairy products because your gut lacks the enzyme needed to break down lactose properly, so you can absorb it.  

Many foods ¡ª such as broccoli and beans ¡ª are known to cause gas. But they do that to almost everyone. Someone with an intolerance is going to be a little more sensitive to certain foods. They¡¯ll experience symptoms after ingesting them that are closer to those of irritable bowel syndrome (IBS). A food intolerance can cause gas, abdominal pain, loose stools and sometimes even nausea. 

IBS is one autoimmune disease that can affect the gut. Others include celiac disease, ulcerative colitis and Crohn¡¯s disease. Since all of these involve some degree of inflammation, their symptoms tend to last much longer.  

With an intolerance or an allergy, you¡¯re usually fine once the offending food is no longer in your system. But if you have a medical condition like celiac disease, in which you absolutely cannot tolerate gluten, your body will let you know very quickly that it is not happy when you¡¯ve ingested some. And once your gut is inflamed, it¡¯s not tolerating much of anything after that. It¡¯s going to take a while for a Crohn¡¯s flare-up to calm down, too.