Tehran University of Medical Sciences Case Reports in Clinical Practice 2538-2683 9 1 2024 10 22 10 16 Mohamad Sadegh Ghasemi Clinical Research of Development Center, Shahid Beheshti Hospital, Qom University of Medical Sciences, Qom, Iran Rasoul Shajari Clinical Research of Development Center, Shahid Beheshti Hospital, Qom University of Medical Sciences, Qom, Iran 2023 12 22 2024 05 28 We reported the case of a 25-year-old woman with antihistamine abuse who presented to our hospital with a GCS of 7 and no significant past medical, psychological, or allergic history. We couldn’t find any evidence of head trauma, seizures, suicide, or any other metabolic, infectious, intoxication, or electrolyte disturbances. During her 10-day admission, the patient developed non-specific manifestations such as fever, hyperthermia, agitation, hypotension, and sinus tachycardia. Physicians should always consider over-the-counter medicines such as antihistamines as a differential diagnosis for loss of consciousness in patients who do not have any footprints of intoxication in primary urine or blood tests. https://crcp.tums.ac.ir/index.php/crcp/article/view/907 https://crcp.tums.ac.ir/index.php/crcp/article/download/907/626