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)
When you have the feeling of freezing then burning sensation all over your body, it usually means that your body is battling a bacterial infection/imbalance. It perhaps may have been something you have eaten during the day. If you only experience hot flashes it may be due to anxiety attacks. Anxiety however will not cause hot and cold flashes to occur. The other cause may be due to the intake of medication; particularly antibiotics. Antibiotics causes your body to lose the correct balance of good and bad bacteria in your body.