Casein is one of the main proteins in cow’s milk. There is casein in the milk of other species (goat, sheep etc.) of a slightly different nature, but the intolerance can carry over in many sensitive people. Therefore, if a casein sensitivity is suspected, you should avoid all dairy products of all species (many people react to supposedly casein-free foods like ghee so we avoid these too). Like gluten, casein sensitivity can also cause symptoms in just about any organ system. Specifically, casein sensitivity can contribute to: ear infections, sinus conditions, asthma, eczema, headaches, arthritis, chronic digestive problems, rhinitis, hay fever, depression, mood swings, ADHD, bedwetting and eczema.