For people whose headaches are mild to moderate and relatively infrequent, this class of medicines (aspirin, acetoaminophen, ibuprofen or naproxen, sometimes combined with caffeine) can be very effective. The danger comes with overuse. When these medications are taken too often or in excess dosing, they result in a chronic, daily headache syndrome known as Medication Overuse Headache (MOH). Overuse can also lead to cardiac, liver and kidney problems. A good rule of thumb for over the counter medicines is "no more than two days per week." If you need treatment more often than this, it is probably time to consult your doctor.