Cluster headaches and migraines sometimes occur on the left side of the head, according to Harvard Health Publications. It is possible for a sinus headache to be on one side, Michigan Headache & Neurological Institute states. In certain cases, a brain aneurysm produces pain on the left side, reports Healthline.
Cluster headaches are characterized by severe pain on one side of the head, HHP says. They occur in groups, often several times a day for a month or more. The pain comes on suddenly, but the headache is typically over in 30 to 60 minutes. Accompanying symptoms are a droopy eyelid and a red, watery eye on the affected side. The nose is often either runny or congested.
Migraine headaches generally begin on one side of the head near the eye and temple, explains HHP. Pain is typically severe and throbbing and gradually extends towards the back of the head. Other symptoms include nausea, watery eye and runny or stuffy nose. Migraines are sometimes preceded by warning signs, or auras, which include flashing lights, wavy lines or numbness on one side of the body.
Sometimes a sinus headache occurs on just the left side of the head because the sinus cavities on that side are congested, according to MHNI. Pain increases when the sufferer bends over or coughs. Other symptoms are a tender and swollen face and nasal discharge. Sinus headaches are typically caused by infection or allergies.
Large or ruptured brain aneurysms sometimes cause pain on one side of the head, states Healthline. When a weak area of an artery fills with blood and swells outward, an aneurysm forms. The pain is often above or behind one eye. In certain cases, a person with an aneurysm has other symptoms, such as light sensitivity, droopy eyelid, double vision, numbness or nausea.