Dryness can be divided into internal dryness and external dryness. Both internal dryness and external dryness (one of the six external pathogens) can cause exhaustion to yin fluids. Symptoms of external dryness include pink eyes, dry sensations in the mouth and nose, dry lips, pain in the ribs, dry cough, and constipation. With internal dryness, the exhaustion of internal yin fluids is mostly due to a later stage of hot diseases or the result of vomiting and diarrhea, excessive perspiration, excessive bleeding, or improper use of drugs. The symptoms of internal dryness consist of hot sensations as if heat were coming from the bones, mental depression, dry lips, dry tongue, dry skin, and dry and withered nails, which are symptoms of yin being harmed by heat.