back pain may also be interpreted as a headache Common causes are tension, migraine, eye strain, dehydration, low blood sugar, and sinusitis. Much rarer are headaches due to life-threatening conditions such as meningitis, encephalitis, cerebral aneurysms, extremely high blood pressure, and brain tumors. Menstruation, experiencing changes in hormone levels, taking a long trip in a car or bus, listening to really loud music, smoking, smelling strong odors such as perfume, smoke, fumes, or a new car or carpet, drinking or eating too much caffeine (in soda, coffee, tea, and chocolate)