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)
Cold sores are caused by the herpes simplex viruses; the most common cause of sores around the mouth is herpes simplex type 1, or HSV-1. Much less commonly, cold sores may be caused by HSV-2 (herpes simplex type 2), which may result from having oral sex with a person who has genital herpes. Cold sores are caused by the herpes simplex virus strain HSV-1. 2  On rare occasions cold sores may be caused by strain HSV-2 - a result of having oral sex with someone who has genital herpes. 3  Cold sores usually clear within 7-10 days without treatment.