Headache is a symptom of various disorders. medically headache is known by the name cephalalgia. headache is due to the changes in the pain sensitive portions in the head.brain is not sensitive to any pain , but some part of head is sensitive to pain.the pain sensitive structures are mainly classified into to two organs inside the cranium and outside cranium. the severe headache are known by the name thunderclap headache. various diseases can cause headache . important among them are described below. meningitis, encephalitis, brain tumor, influenza, temporal arteries, lyme disease, sinusitis, mononucleosis, glaucoma,mononucleosis, severe hypertension,hashimoto’s thyroiditis,rubella, strep throat, small pox, common cold,mumps, lassa fever etc.

most of the head ache are harmless these are primary headache. some headache are more severe, which is the indication of some serious diseases. these headache treated as secondary. it is very difficult to differentiate primary and secondary headache. neuro imaging technique are used to differentiate these two.
for treatment we can use paracetamol, aspirin, diclofenac etc.