Cold is one of the yin external pathogenic energies that can easily cause harm to yang energy. When a person's yang energy is deficient, defense energy will fail to guard the body against foreign invasion. Cold energy will attack, giving rise to such symptoms as dislike of cold, fever, headache, pain in the body, pain in bones and joints, and abdominal pain with diarrhea.
Like wind, cold can be divided into external and internal types. External cold refers to the cold energy that attacks the body from the outside. External cold causes a blockage of yang energy, with such symptoms as dislike of cold, fever, absence of perspiration, headache, pain in the body, and superficial and tight pulse. External cold can also refer to a weakening of yang energy in the body, with such symptoms as fear of cold and being very susceptible to an attack of the common cold. Internal cold refers to a weakening of yang energy, with a decline in organ functions that may give rise to disturbances of water transformation, retention of urine, and the like.
There can also be a direct attack of cold. Referred to as cold stroke, this is when the cold pathogenic energy attacks while the person is suffering from yang deficiency. The symptoms may include cold limbs and deep and fine or slow and tight pulse.