There are no specific four diseases that need to be alerted to the left side headache in men. Left side headache can be caused by a variety of diseases, such as primary headache and secondary headache. 1. Primary headache: tension headache, migraine, cluster headache and other primary headache can lead to the appearance of the left side of the migraine, can be induced by food, medication, insufficient rest, fatigue and other factors. 2. Secondary headache: cerebrovascular lesions such as cerebral infarction, intracranial space-occupying lesions such as brain tumor, left-sided cerebral contusion or hematoma, skull fracture, trigeminal nerve injury, acute otitis media and other ear diseases may cause left-sided headache. When it is not relieved after resting, early diagnosis and treatment should be made to avoid delaying the condition.