Updated: Apr 13, 2022
A lot, actually. Under the microscope, layers of the skin and intestinal lining look very similar. Both serve similar functions, protecting you from the outside environment by not letting a lot of harmful substances pass through and get into your body.
The protective function of the skin and intestine are further enhanced by your body’s defense system being at-the-ready in both places. Allergic reactions to foreign substances can be protective but also can result in itchy rashes or gastrointestinal symptoms like belly pain, diarrhea and/or constipation. In fact, recent medical studies suggest your skin and intestinal lining may react to the same substance. This observation has proven useful in that an allergy test on the skin has been shown to help identify food allergies that trigger irritable bowel syndrome (IBS). Skin patch testing, traditionally used in dermatology to evaluate some skin rashes, can now be used to identify these food allergies. When the foods identified are removed from the diet, IBS symptoms often improve or completely resolve. The theory being that an allergic reaction similar to that caused by food patch tests likely occurs in the intestinal lining when the same food is eaten, causing the IBS symptoms.