Cold feet can occur for a variety of reasons. The most common causes of cold feet involve the circulatory system in some form. The body has an automatic thermostat built into the nervous system that senses the general temperature of the surrounding environment. When the surrounding temperature is warm, the body will increase blood flow to the arms and legs to dissipate heat from the body core. The opposite occurs when it is cold, as the body will limit blood flow to the arms and legs to preserve heat. The end effect of this is colder hands and feet as a result of this limitation of blood flow. In some individuals, the presence of a condition called Reynaud's disease even further limits blood flow to the hands and feet, leading to abnormally cold, purple or blue colored, and sometimes painful fingers and toes. In this condition, the fingers and toes are much colder than they should be, and this can be one of the causes of abnormally cold feet.
Another more serious cause of cold feet as it pertains to the circulatory system is actual poor circulation due to artery blockage. Peripheral arterial disease is common, under diagnosed, and potentially can lead to amputation of the leg when severe and untreated. This condition develops when blockage forms in the inner wall of the arteries delivering blood to the legs, or when calcification forms in the muscle tissue surrounding the inner artery wall. As the warm blood is blocked from entering the foot at full capacity, the actual temperature of the foot skin will decrease, leading to actual cold feet. Unfortunately, this condition does not go away when the weather warms, and requires a vascular surgeon or interventional cardiologist to restore circulation to the legs.
Related to artery blockages is a condition called an arterial embolism. An embolism is a piece of tissue that travels down the bloodstream and becomes clogged in the wall of an artery that is too small for the piece to travel through. This effectively blocks off the circulation downstream, like a dam to a river. This tissue often comes from the heart, where vegetation can grow on diseased heart valves, as well as from loose artery wall blockages further upstream. The result is lack of blood flow further on down the leg, foot, or toe, depending on the size of the embolism and where it became stuck. A cold foot may be one of the many symptoms of this condition.
Other causes of cold feet include medications, as well as various diseases involving the hormonal and immune systems. Cold feet can be the result of certain heart medications, like beta-blockers, as well as some migraine medications and certain cold medications that contain pseudoephedrine. Abnormalities with the thyroid gland, the adrenal gland, and disease of connective tissue due to an autoimmune disease (lupus, etc.) can all produce cold feet.
Some diseases don't actually cause the foot to be colder, but the sensation of an icy cold foot is present even though the foot temperature itself is normal. These diseases include peripheral neuropathy, in which the nervous system, particularly sensation, is behaving abnormally. Common in diabetics and those with spinal disease, this condition produces a sensation of the foot feeling numb and cold. Other diseases causing an abnormal sensation of coldness despite normal skin temperatures include fibromyalgia and tarsal tunnel syndrome, a nerve entrapment disease in the ankle region.
Treatment of cold feet vary greatly according to the actual underlying condition. Simple cases of air temperature-related foot coldness can be treated with warm socks and limited exposure to colder air. Artery blockages and emboli need the care of a vascular specialist, and medication/medical causes need to be addressed individually. Nerve-related causes of false cold sensation can be treated with specialty medication, or surgery if there is pressure on the nerve (such as in back disease or tarsal tunnel synrome).