Extreme cold can often feel remarkably similar to intense heat, a perplexing sensation known as “cold burn.” This common experience highlights the complex ways our bodies perceive environmental stimuli. Understanding why cold can feel like burning involves exploring the intricate mechanisms within our nervous system and the physical effects on our cells.
The Sensory Paradox
Our perception of temperature and pain relies on specialized nerve endings in the skin and mucous membranes. These include thermoreceptors, which detect temperature, and nociceptors, which are pain receptors. Both extreme heat and extreme cold can activate these nociceptors, sending signals to the brain that are interpreted as pain.
Specific transient receptor potential (TRP) ion channels play a role in sensing these temperature extremes. For instance, TRPV1 channels are activated by noxious heat, typically above 43°C, and also by compounds like capsaicin found in chili peppers. Similarly, TRPM8 channels are sensitive to cold temperatures, active at or below 25°C, while TRPA1 is thought to respond to temperatures near the point where cold becomes painful, around 15°C. When exposed to extreme cold, the intense activation of these cold-sensitive channels, particularly those that also respond to noxious stimuli, can trigger the same pain pathways as extreme heat.
The brain receives these strong signals from nociceptors, which are designed to warn the body of potential tissue damage. Because the neurological signals produced by extreme cold are similar to those from a severe burn, the brain interprets the sensation as burning. This shared processing mechanism explains why a dangerously cold stimulus can elicit a sensation so akin to being burned.
Cellular Impact of Extreme Cold
Beyond the sensory experience, extreme cold can inflict actual physical damage at the cellular level. When tissues are exposed to temperatures below freezing, the body initiates a protective response called vasoconstriction. This narrowing of blood vessels reduces blood flow to the affected area, attempting to conserve heat in the body’s core. While beneficial for core temperature, prolonged vasoconstriction can deprive peripheral tissues of oxygen and nutrients, leading to injury.
A significant mechanism of cold-induced cellular damage is the formation of ice crystals. As water within and around cells freezes, these crystals can grow, physically puncturing cell membranes and disrupting cellular structures. The formation of ice outside cells also draws water out of the cells, leading to cellular dehydration. This increased concentration of solutes within the remaining unfrozen water can further damage cellular proteins and functions.
Both intracellular and extracellular ice formation contribute to cell death and tissue injury. Even after rewarming, the damage sustained from these processes can result in cell death and tissue necrosis, commonly seen in conditions like frostbite. The cellular destruction from extreme cold, though mechanically different from heat, produces a comparable outcome in terms of tissue damage.
Common Experiences of Cold Burn
The “cold burn” sensation manifests in several common experiences. One familiar example is “brain freeze,” scientifically known as sphenopalatine ganglioneuralgia, which occurs when very cold food or drink rapidly cools the roof of the mouth. This sudden temperature change causes blood vessels in the mouth and head to constrict and then rapidly expand, activating pain receptors and sending signals via the trigeminal nerve, resulting in a sharp headache.
Touching dry ice, which has a temperature of about -78.5°C (-109.3°F), produces an immediate burning sensation. This is cellular destruction from rapid freezing. The extreme cold causes water within skin cells to freeze and form ice crystals, tearing cell walls and causing damage akin to a thermal burn.
Similarly, contact with very cold metal can result in a “cold burn” because metals are excellent conductors of heat. When bare skin touches cold metal, heat rapidly transfers from the skin to the metal, causing quick localized cooling that can freeze the water in skin cells, leading to cell damage and a burning sensation.