Like all body parts, the surface of the legs can become cold under certain conditions. To prevent this we may cover the legs and feet, relocate towards a warm environment and move the legs to generate heat. The body may also reroute heat from the torso to the legs to help control its temperature. However, there are cases where the legs become cold and there is an ache or pain associated with coldness despite the best attempts to keep warm.
Why do the legs get cold?
The legs are more likely than other parts of the body to become cold if left uncovered. The toes, feet and lower legs are particularly prone to this coldness even if there are no underlying medical problems. In order to understand why the legs become cold so quickly and easily, it is first important to understand how the body maintains temperature – both the internal temperature and the surface temperature.
The internal temperature refers to the area under the skin, including the blood and ‘flesh’. The surface temperature refers to the skin that is exposed to the outside environment. The body is constantly generating heat but losing it to the environment. This is balanced by the thermoregulatory mechanisms to ensure that the internal body temperature stays as close to 37ºC.
The surface temperature of the body is partly determined by the internal temperature and also in part by the environmental temperature. Cooling is achieved through widening of the surface blood vessels to allow heat to dissipate and with sweat that evaporates from the skin surface. For heating, the surface blood vessels narrow to preserve heat while more blood is routed to the area since blood carries heat from the torso.
Therefore coldness of the legs may be due to excessive cooling and insufficient heating. With the lower legs, feet and toes being the farthest parts of the body from the torso, heat may be lost during its travel to these areas. However, it is important to differentiate coldness from an actual low temperature in/on the legs and just a sensation of coldness despite the temperature being normal.
Pain and Other Symptoms
Coldness of the legs is a symptom and may be accompanied by other signs and symptoms. One of the common accompanying symptoms is an ache or pain. Most of the time pain due to cold is described as a deep ache or cramping pain. Cold can also aggravate pain that may be pre-existing. For example, people with joint pain due to conditions like rheumatoid arthritis may experience worsening of the pain with coldness.
There may be other symptoms that accompany the cold sensation and pain. This may include paleness of the legs and sometimes even a bluish tinge, loss of hair, lacerations (cuts), open sores (ulcers) and skin rashes. There may also be loss of sensation such as the ability to perceive touch or temperature. Depending on the nature of the underlying condition there may also be weakness of the legs and even paralysis.
Read more on pale legs.
Causes of Cold Legs
Cold legs may be due to physiologic or pathologic reasons. Physiologic refers to normal mechanisms and processes whereas pathologic means diseases and disorders. It is important to first exclude physiologic reasons for cold legs before looking at pathologic reasons. Many of the causes of cold legs are the same as the causes of cold hands.
Read more on cold hands.
Naturally the legs will be cold if the environment is cold. As explained above, the lower parts of the legs are more prone to becoming cold than other parts of the body due to its distant from the heat-generating torso. In addition, the long narrow structure of the legs also means that more are flows around thereby cooling it faster. Therefore the legs need to be carefully insulated and protected in cold climates.
In severe climatic conditions such as with exposure to snow, the legs and feet may sustain cold injuries such as frostbite. If the entire body is affected then it can lead to hypothermia. However, loss of body temperature can also arise with prolonged exposure to wind and immersion in water.
Since blood carries heat to the legs from the torso, any disruption of this blood flow can lead to abnormal coldness of the legs. This may be seen with conditions like peripheral vascular disease which is a narrowing of the artery that carries blood to the legs. It may be due to plaques in the artery wall, spasm of the arteries like in Raynaud disease, inflammation of the artery wall and damage to the blood vessel wall with conditions like diabetes.
The heart is responsible for distirbuting the blood throughout the body. Therefore diseases that lead to weakening of the heart can compromise blood flow to the legs, such a aheart attack or heart failure. Similarly the veins need to carry blood away from the legs and back to the heart. If these veins are weak or damaged, then blood may pool in the legs and affect circulation.
Significant blood loss can also affect heat distribution to the legs as may be seen with hypovolemic shock.
Nerves control the widening and narrowing of the blood vessels in the legs as well as sweating. If these nerves are damaged or diseased then the blood flow to the legs can be affected. Furthermore the temperature regulation of the body is controlled by the hypothalamus which determines the core body temperature. This can be seen with conditions like peripheral neuropathy (nerve disease) which can occur with diseases like diabetes or a stroke.
The body generates heat as a result of biochemical processes that occur in every cell. The higher the metabolic activity the more heat that is generated. Metabolism is influenced by a host of different factors such as nutrition, oxygen levels, hormones and nerve stimulation. Therefore problems with these metabolism-regulating factors can lead to a low body temperature, although this may not always be isolated to the legs.
This may be seen in conditions such as:
- Addison’s disease
- Diabetes mellitus
- Iodine deficiency
Drugs and Other Substances
A number of different substances can affect the metabolism, blood flow and nerve activity. This includes medication, illicit drugs and alcohol. Poisoning with any toxic substance can also lead to coldness as the body due to various different mechanisms which can lead to death depending on the dose.
Most of these substances affect the core body temperature or blood flow throughout the body and not just of the legs. Since the legs are more likely to become colder to a greater degree than the rest of the body, coldness of the legs may therefore be more prominent.