Increased bodily temperature from Diphenhydramine

Increased bodily temperature, clinically termed hyperthermia or pyrexia, refers to an elevation of core body temperature above the normal baseline of approximately 37C (98.6F). In the context of psychoactive substance use, this effect can range from a barely noticeable mild warmth to a life-threatening medical emergency when body temperature exceeds 40C (104F) and especially above 41.5C (106.7F), at which point organ damage, seizures, and death become real possibilities. This makes hyperthermia one of the most genuinely dangerous physical effects associated with substance use.

The mechanisms of substance-induced hyperthermia are multiple and often compounding. Stimulants and empathogens (MDMA, methamphetamine, cocaine) increase metabolic heat production through catecholamine-driven increases in basal metabolic rate, while simultaneously impairing the hypothalamic thermoregulation center's ability to initiate cooling responses (vasodilation, sweating). MDMA is particularly dangerous because it additionally impairs the body's thermal set-point through serotonergic mechanisms.Environmental factors — hot, crowded venues, sustained dancing, inadequate hydration, and lack of cooling breaks — compound pharmacological hyperthermia dramatically. Most MDMA-related fatalities involve the combination of the drug's thermogenic effects with the environmental heat load of all-night dancing in warm venues.

Serotonin syndrome represents the most extreme form of substance-induced hyperthermia, where the body temperature can spike rapidly to 41C+ (106F+) due to uncontrolled serotonergic neuromuscular activation generating massive amounts of metabolic heat. The combination of MAOIs with MDMA, SSRIs, or dextromethorphan are the highest-risk scenarios for this type of catastrophic hyperthermia. Even without full serotonin syndrome, heavy doses of serotonergic substances in hot environments can produce dangerous temperature elevations.

Harm reduction note: Temperature management is one of the most critical aspects of stimulant and empathogen harm reduction. Take regular cooling breaks from dancing. Move to cooler areas. Hydrate steadily (but not excessively — hyponatremia from overdrinking water is also dangerous with MDMA). Monitor yourself and friends for signs of overheating: excessive sweating that suddenly stops (a dangerous sign that the thermoregulation system has failed), confusion, hot and dry skin, or muscle rigidity. A rectal or temporal temperature reading above 39.5C (103F) during substance use warrants immediate active cooling (cold water, ice packs to neck/armpits/groin) and medical attention. Above 40.5C (105F) is a medical emergency — call for help immediately.