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)
What causes cold sores? Cold sores are caused by herpes simplex virus 1 (HSV-1), the oral form of the virus. In fact, 67% of the world population under age 50 has HSV-1 because it is so contagious.1 Once you are infected, the virus never leaves your body. Most people arenât exactly sure when they first encountered the virus.