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)
So it's still the virus, not the cold air, that's causing you to fall ill. There have been a lot of studies done, but really there's still no evidence to show that it's the cold weather itself that's making us sick, Dr. Garg said. It's sort of coincidental that certain viruses flare up this time of year.. In the spring, seasonal sniffing can also come from another culprit: allergies.