Hello, Primary headaches are stand-alone illnesses caused directly by the overactivity of, or problems with, structures in the head that are pain-sensitive. This includes the blood vessels, muscles, and nerves of the head and neck. They may also result from changes in chemical activity in the brain. Common primary headaches include migraines, cluster headaches, and tension headaches. Secondary headaches are symptoms that happen when another condition stimulates the pain-sensitive nerves of the head. In other words, headache symptoms can be attributed to another cause. A wide range of different factors can cause secondary headaches. These include: concussion, dehydration, glaucoma, teeth-grinding at night, influenza, overuse of pain medication, known as rebound headaches, panic attacks, stroke. As headaches can be a symptom of a serious condition, it is important to seek medical advice if they become more severe, regular, or persistent. Consult your clinician immediately alcohol-induced hangover, brain tumor, blood clots, bleeding in or around the brain, brain freeze, or ice-cream headaches, carbon monoxide poisoning. Hope I have answered your query. Let me know if I can assist you further. Take care Regards, Dr AJEET SINGH, General & Family Physician