The sensation of feeling both hot and cold at the same time signals a temporary or chronic disruption in the body’s internal temperature control system. This phenomenon typically involves feeling flushed, sweating, or internally overheated while simultaneously experiencing chills, goosebumps, or shivering. It is not a contradiction but rather a sign that the body’s temperature regulation mechanisms are struggling to maintain a stable internal state. The body is effectively in a state of conflict, trying to warm itself and cool itself down simultaneously or in rapid succession. Understanding the root cause requires looking at how the body manages its temperature and what factors can interfere with this delicate balance.
How the Body Regulates Temperature
The body maintains a core temperature of approximately 98.6°F (37°C) through thermoregulation, primarily managed by the hypothalamus in the brain. This area functions as the body’s thermostat, constantly receiving signals from temperature sensors and adjusting for any deviation from the set point. When the body needs to cool down, the hypothalamus triggers mechanisms like vasodilation (where blood vessels near the skin widen to release heat) and sweating (where evaporation cools the surface).
Conversely, when the body needs to generate heat, the hypothalamus initiates vasoconstriction, narrowing blood vessels in the skin to conserve warmth near the core. Shivering, which involves rapid, involuntary muscle contractions, is another primary response used to generate heat metabolically. The simultaneous feeling of being hot and cold often occurs when the body’s set point is suddenly altered, such as during a fever, creating a mismatch between the internal temperature and the desired temperature.
Causes Related to Acute Illness and Immune Response
The most common reason for feeling cold and hot simultaneously is the body’s response to an acute infection, often presenting as a fever. When the immune system detects a pathogen, it releases chemical messengers called pyrogens. These pyrogens travel to the hypothalamus and “reset” the body’s temperature set point to a higher level, typically above 100.4°F (38°C).
Because the body’s current core temperature is now below this new, higher set point, the hypothalamus perceives the body as being too cold, even though the temperature is rising. This triggers the cold phase, leading to intense chills, shivering, and peripheral vasoconstriction to generate and conserve heat. Once the immune system begins to overcome the infection, the production of pyrogens stops, and the hypothalamic set point rapidly returns to the normal range.
At this point, the body’s core temperature is significantly higher than the new, lower set point, causing the person to feel intensely hot. The hypothalamus then activates its cooling mechanisms, resulting in vasodilation and profuse sweating, which is a sign that the fever is “breaking.” This cycle of shivering chills followed by drenching sweats is a pattern of the immune system fighting off infections like the flu, a urinary tract infection (UTI), or strep throat.
Hormonal Changes and Systemic Conditions
Beyond acute illness, many non-infectious, systemic conditions can interfere with the body’s thermal regulation. Hormonal fluctuations are a frequent cause, particularly in women experiencing perimenopause or menopause. Hot flashes and night sweats are caused by a dysfunction in the hypothalamus, which is hypersensitive to even minor changes in body temperature due to fluctuating estrogen levels. This sudden, intense feeling of heat and sweating is often immediately followed by a rapid drop in temperature, leading to a sensation of cold or chills.
Disorders of the endocrine system, such as hyperthyroidism, can also cause temperature dysregulation. An overactive thyroid gland produces an excess of thyroid hormone, which speeds up the body’s entire metabolism and increases heat production. This constant internal overheating can result in heat intolerance and excessive sweating, which may alternate with chills if the body overcompensates in its cooling efforts. Additionally, the body’s stress response, triggered by anxiety or panic, can cause sudden temperature shifts.
The “fight-or-flight” response releases hormones like adrenaline, which can cause blood vessels to constrict in the extremities, leading to cold hands and feet while the core feels hot and sweaty. Certain medications, including some antidepressants and opioids, can also disrupt the central nervous system’s control over body temperature as a side effect. Neurological conditions, like Multiple Sclerosis, can directly damage the nerve pathways that transmit temperature signals to the brain, impairing the ability to regulate heat and cold effectively.
When This Symptom Requires Medical Attention
While many instances of alternating hot and cold sensations relate to a common, self-limiting illness, certain accompanying symptoms warrant immediate medical evaluation. Seek professional care if the fever is high, typically exceeding 103°F (39.4°C), or if it is rapidly rising and cannot be managed with standard over-the-counter medication. Prolonged temperature swings that persist for more than a couple of days without a clear cause also require investigation to rule out an underlying issue.
Red flag symptoms that signal a potentially serious condition include a stiff neck, severe headache, confusion, or difficulty breathing. The inability to keep fluids down, which can lead to dehydration, is another reason to consult a healthcare provider promptly. For individuals experiencing chronic, unexplained temperature sensitivity that begins to interfere with daily life, a medical assessment can help identify systemic causes, such as thyroid dysfunction or a nervous system disorder.