When the heat is excited after the face skin black, may be the face of blood vessel expansion, blood volume increased, can be considered to be sensitive skin, hormone-dependent dermatitis, etc., the specific conditions need to be analyzed specifically. 1. Sensitive skin: the more sensitive skin of the crowd, in the face of hot excitement when the capillary expansion is obvious, easy to lead to the face of the increase in blood volume, caused by the face of the red or even purple, may show the skin blackened situation. 2 hormone-dependent dermatitis: due to the long-term use of hormone-containing ointments or cosmetics leading to thinning of the facial skin, capillary expansion and other conditions, in the heat of the excitement will also make the facial skin red, purple, may be manifested as a darkening of the situation. There are many reasons why the skin on the face turns black after being agitated by heat, in addition to the above reasons, lack of sleep, prolonged exposure to the sun, etc., are also prone to this condition, and it is recommended that you go to a professional skin hospital in a timely manner.