Headache pain can start in different structures in the head. The brain itself doesn't hurt, but other parts of the head do. Headaches can happen without seeming to be linked to any illness. These are known as primary headaches. Examples of primary headaches include migraine, cluster, and tension headaches.

Some causes of headache are:

• Blood vessels that become enlarged (dilated) or constricted.
• Muscles in the neck and head that become tight or tense.
• Muscles around the eyes that become strained because of overwork or poor vision correction.
• Sinuses that become swollen because of allergies, colds, or infections.
• Teeth that are decayed or damaged.
• Nerves that transmit abnormal pain signals.
• Joints in the jaw and neck that are overused or become damaged.

Referred pain has its source in one place, but is felt in another. For instance, pain behind the eyes may actually be caused by tense muscles in the neck and shoulders. This means that the place that hurts may not be the part of the head that needs treatment.

Seek care now or call 911 if:

• You have the worst headache you have ever had or a severe headache that starts suddenly.
• You have a headache with:
  • Trouble talking or seeing
  • Extreme drowsiness, confusion, or fainting
  • Balance, numbness, or weakness
• You have had a head injury.