All warm-blooded organisms, we have the ability to maintain our internal body temperature through various mechanisms. However, most of us prefer a narrow range of temperatures and will take additional measures, like dressing warmly or sitting in an air conditioned room, if the environmental temperature rises or falls below a certain comfort level. Some people, however, are unusually intolerant and sensitive to cold.
What is cold sensitivity or cold intolerance?
Cold sensitivity simply means that a person feels uncharacteristically cold compared to others. It is synonymous with cold intolerance. However, people who are intolerant to cold will take various measures to stay warm and avoid cold even when the environmental temperature is not uncomfortably cold to others. This can be a symptom of various diseases, apart from just individual sensitivity.
The measures a person may take can seem out of character or even be classified as abnormal behavior when compared to others in the same setting. In extreme cases, a person who is cold sensitive or intolerant may be dressed with heavy warm clothing even on a hot day. These measures can be dangerous as a person may become overheated and this could even lead to death, particularly in hot environments.
Hot and Cold Temperature Regulation
Normal metabolic activities, meaning energy production by all cells in the body, produces heat as a byproduct. The normal body temperature is maintained around 37ºC (98.6ºF). When the core body temperature rises beyond the narrow temperature range that is considered normal, thermoregulatory mechanisms take effect.
The surface blood vessels dilate and heat from deeper lying parts of the body is passed out into the environment. This is further expedited by sweating, as the evaporation of the sweat from the skin surface has a cool effect. In these cases of overheating, a person will feel uncomfortable in hot environments and warm clothing and will make appropriate adjustments.
On the other hand, when the body temperature drops below the normal levels metabolic activity may increase to raise the core temperature. Shivering is one of the ways this is achieved, as the rapid contraction and relaxation of muscles requires more energy and heat is produced. Similar to feeling hot, a person will seek warmer clothing and warmer environments to feel comfortable.
Causes of Cold Sensitivity and Intolerance
Individual tolerance to cold and heat varies. It is mainly due to conditioning. A person who lives in a colder environment will naturally be accustomed to these temperatures as would a person who lives in a hotter environment. However, there is a limit to these individual tolerances.
It is important to understand that mammals feel cold in what would be considered a cold environment. While it is said that the most comfortable temperatures for humans ranges between 20º to 25ºC (68º to 77ºF), many people will still fell comfortable a few degrees below or above these levels.
Physical differences among people like body fat concentration also plays a role as it acts as an insulator on the skin surface. Some people naturally feel colder than others for no specific reason, although this is usually a significant difference. People who are ill, babies and the elderly may be sensitive or intolerant to cold and this could be due to abnormalities or short term physiological alterations with temperature regulation.
Hypothermia is an abnormal and excessive drop in core body temperature. It can vary in severity and is usually associated with cold exposure, including immersion in cold water. However, hypothermia may also arise with the use of certain drugs, alcohol, heart failure, stroke, anemia, endocrine diseases, poisoning, mental illnesses, liver failure and lung infections.
Hypothyroidism, or an underactive thyroid gland, leads to a reduction in metabolic activity since the thyroid hormones influences metabolic rate. This reduced metabolic activity leads to less efficient energy production and therefore a slight reduction in body temperature. Cold sensitivity and intolerance is a prominent symptom in hypothyroidism although it does depend on the severity of thyroid hormone deficiency.
A fever is a common sign associated with various infections. Although the body temperature rises with a fever, a person will often feel uncharacteristically cold. This is due to an alteration in the thermoregulatory mechanisms in the brain. The cold sensitivity and intolerance often drives a person to seek warmth, be it from an external source of with warmer clothing, further driving up the body temperature.
Fever of Unknown Origin
Fevers most commonly arise with infections but can also arise for other reasons, like with certain autoimmune diseases. However, there are cases where the cause of a fever cannot be identified despite extensive medical investigations. These types of fevers are termed fever of unknown origin (FUO). As with a fever due to identifiable causes, a person may feel cold despite the increase in body temperature.
Temperature control within the body is regulated by the central nervous system (CNS) and specifically the hypothalamus, an area in the brain. If there is an disease or damage to this area, it can affect temperature control and also alter temperature sensitivity. This may be seen with traumatic brain injury, infections like meningitis or encephalitis, the use of certain drugs that act on the brain and sometimes with mental health conditions.
A number of different drugs can affect temperature sensitivity and tolerance through various mechanisms. It may affect the temperature control center in the brain, reduce metabolic activity or trigger cooling mechanisms prematurely that causes a drop in body temperature. Drugs like hypnotics, tranquilizers and sedatives can even cause hypothermia. Alcohol and illicit substances can also have this effect.
There are a number of circulatory conditions where a person may feel cold for various reasons. The heart and blood vessels play an important role in distributing heat throughout the body, especially to the surface from deeper lying areas. Therefore if the heart is under-functioning like with heart failure or if the blood vessels are not allowing for normal blood flow like with Raynaud’s disease, a person may feel uncharacteristically cold.