One strange cause of headaches: Headaches such as these usually come on 2-3 days before the disaster (depending on how severe it will be) and leave after the event happens. When earth changes happen, I feel irritable, weepy, dizzy (for earthquakes that happen around the world larger than 5 on the Richter scale) and sometimes I can’t sleep for a night or two before the disaster happens.
For headaches and migraines, detection of food allergies depends on whether your body is allergic, intolerant and what time it was eaten. Some symptoms can show up within minutes, other symptoms within 36 hours. Muscle-testing will pick up those foods that are a problem for you lately, but not always from way back in the past. I can muscle-test out an approximate time period when the headache will come on after you eat a specific food. This often seems quite helpful for my headache-suffering clients.