A leaky gut is when the delicate mucous membrane lining the small intestine becomes unhealthy (too permeable) and allows proteins to cross. These unknown proteins in the blood trigger an inflammatory response because the immune system thinks they are a threat. This is the cause of food insensitivities or intolerances. 

Is there a solution to leaky gut?

This can be resolved by cutting out offending food to heal the gut and paying attention to the digestion process. Dairy, gluten and/or nightshades for example, are known to cause digestion issues.