A check valve, clack valve, non-return valve or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave.
Some causes of cold intolerance are: 1  Anemia. 2  Anorexia nervosa. 3  Blood vessel problems, such as Raynaud phenomenon.  Chronic severe 1  illness. General poor health.  Underactive thyroid 1  (hypothyroidism) Problem with the hypothalamus (a part of the brain that controls many body functions, including body temperature)
One example of this problem is hot and cold flashes. Hot and Cold Flashes = Anxiety? Anxiety excites your sympathetic nervous system in the same way as hormonal fluctuations. That excitement causes your body to heat up, and then cool down. But hot flashes are rarely the only symptom. Click here to see if your hot and cold symptoms are likely due to anxiety. Hot Flashes and Health