The sensation of feeling hot and cold simultaneously or in rapid succession indicates a temporary failure in the body’s temperature control system. This symptom, often presenting as cyclical chills followed by sweating, signals that the body is struggling to maintain its internal temperature within a narrow, healthy range. The experience is not necessarily due to a high or low core temperature, but rather a mismatch between the desired temperature set point and the actual temperature being sensed. Understanding the mechanisms of thermoregulation explains why this disorienting feeling occurs.
The Science of Thermoregulation
The body maintains a core temperature near 98.6°F (37°C) through thermoregulation, centered in the hypothalamus. This brain region acts as the body’s thermostat, constantly receiving signals from temperature sensors. When the core temperature rises, the hypothalamus triggers heat dissipation responses, such as vasodilation (widening blood vessels near the skin) and activating sweat glands. If the temperature drops, it initiates mechanisms to conserve and generate heat. Conservation involves vasoconstriction, shunting blood away from the skin, while generation includes shivering, which rapidly contracts muscles to produce heat. The feeling of being hot and cold often results from the body rapidly switching between these opposing heat-loss and heat-gain responses.
Acute Changes: Infection and Immune Response
The most common cause of the hot and cold sensation is the body’s acute immune response to an infection, resulting in a fever and the classic cycle of chills and sweats. When pathogens enter the body, immune cells release signaling molecules called pyrogens. These pyrogens travel to the hypothalamus, triggering the production of prostaglandin E2 (PGE2), which resets the thermostat to a higher temperature set point. Because the actual body temperature is now below this new set point, the hypothalamus perceives the body as too cold. This initiates extreme heat-generating measures, including intense vasoconstriction and shivering, experienced as deep chills. Once the body temperature reaches the elevated set point, the chills stop and the person feels hot and flushed. The cycle reverses when the set point drops back to normal, either due to the immune system or medication. The body, now overheated relative to the lower set point, must rapidly lose heat. This is accomplished through aggressive vasodilation and profuse sweating, experienced as the fever breaking, which can leave a person feeling cold and clammy due to rapid evaporative cooling.
Chronic Imbalances: Hormonal and Metabolic Factors
Long-term disruptions to metabolic or hormonal systems can lead to chronic temperature instability.
Thyroid Function
The thyroid gland produces hormones that regulate the basal metabolic rate (BMR), influencing heat production. Hyperthyroidism (overactive thyroid) increases the BMR, causing excess heat generation and intolerance of warm environments. Hypothyroidism (underactive thyroid) slows metabolism, resulting in reduced heat production and persistent cold sensitivity.
Menopause and Hot Flashes
Hormonal shifts during menopause frequently cause intense, rapid temperature shifts known as hot flashes (vasomotor symptoms). The decline in estrogen affects the hypothalamus, narrowing the “thermoneutral zone” between sweating and shivering thresholds. This hypersensitivity means a minor increase in core temperature triggers an exaggerated heat dissipation response, involving sudden vasodilation and drenching sweat. The resulting rapid heat loss often leads to a subsequent chill as the body overshoots its cooling target.
Hypoglycemia
Metabolic changes, particularly hypoglycemia (low blood glucose), also trigger a hot and cold response. When blood sugar drops too low, the body releases counter-regulatory stress hormones, primarily epinephrine (adrenaline), to mobilize glucose reserves. This surge activates the sympathetic nervous system, causing symptoms like a rapid heart rate, shakiness, and profuse sweating. The combination of internal stress and the skin-cooling effect of the sweat is often felt as a sudden cold sweat or clamminess accompanied by chills.
Environmental and Stress-Related Triggers
Stress and Anxiety
External factors and psychological stress can hijack the body’s thermoregulation mechanisms, leading to sudden temperature sensations. Conditions like anxiety and panic attacks activate the sympathetic nervous system’s “fight-or-flight” response. This immediate response causes peripheral vasoconstriction to conserve blood for major muscle groups, initially creating a feeling of coldness in the extremities. The heightened metabolic state and rapid changes in blood flow then trigger a secondary cooling response, resulting in a sudden wave of heat and sweating. The conflicting signals from the nervous system can result in the sensation of being both hot and cold.
Medication Side Effects
Certain medications can impair the body’s ability to manage temperature by interfering with the hypothalamic set point or disrupting cooling functions. Medication classes with anticholinergic properties, such as some antidepressants, can inhibit sweat production, preventing effective cooling. Stimulant medications, including those for ADHD, can increase the metabolic rate, generating excess body heat. Additionally, some blood pressure medications, like beta-blockers, can reduce blood flow to the skin, limiting heat dissipation through vasodilation.