Why Do I Have a Headache on the Left Side of My Head?

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A headache on the left side of your head can be due to a primary headache disorder, like migraine or cluster headache. It can also occur due to an injury like a concussion, lifestyle factors like diet or insufficient sleep, or a condition such as allergies, high blood pressure, or stroke.

Some of these can be self-managed, while others may need the help of a healthcare practitioner—in some cases, urgently. The fact that the pain is only on the left side of your head offers them clues as to what's going on.

This article will go over what causes left-sided headaches and how to manage this condition.

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Left-Sided Headache Causes

Clinically referred to as “unilateral headaches,” headaches on one side of the head arise due to a variety of factors. Everything from lifestyle choices to head injury can be at fault. Here’s a breakdown of common causes of left side headaches.

Lifestyle Contributors

Some one-sided headaches arise due to lifestyle factors. Understanding these connections can be a way of preventing and minimizing the impact of this issue. Common factors that can bring these issues on include:

  • Diet: A common reason people develop headaches is skipping meals. With migraines, certain foods and drinks can trigger attacks.
  • Sleep: Getting insufficient rest at night and having an inconsistent sleep schedule are linked to migraines and headache.
  • Stress: Stress and tension are migraine triggers.
  • Environmental factors: Things like air pollution and odors, bright light or flashing lights, or even shifts in weather patterns can all bring on headaches.
  • Physical exertion: While regular exercise helps prevent headaches, overexerting yourself can also be a means of bringing on headache attacks.

Common Health Conditions

A variety of common health conditions can cause headaches. These include:

  • Sicknesses: Infection of the sinuses, or sinusitis, can cause inflammation on one or both sides of the head. If only one sinus is affected, the pain will only be felt on that side of the head. In addition, headaches often accompany viral infections, such as the common cold and influenza (flu). The fever produced by these conditions can be another cause of unilateral headaches.
  • Allergies: Headaches on the left side of the head can also accompany allergies. This happens as certain foods, drinks, and environmental stimuli set off your body’s immune response, which inflames the sinuses, causing pain in the forehead and cheeks.
  • Concussion: Minor traumatic brain injury (mTBI), or concussion, can also be a cause of unilateral headache pain. This happens when a blow, sudden jolt, or impact to the head causes the brain to twist or hit the sides of the cranium (or skull). These are potentially very dangerous and require prompt medical attention.
  • High blood pressure: Also known as hypertension, high blood pressure often doesn’t cause any symptoms. However, symptoms, including headaches, do arise in some cases. This condition can also cause dizziness and shortness of breath.

Monitoring Your Blood Pressure

High blood pressure can lead to stroke, heart disease, and other serious health issues. This is why it’s important to know what your blood pressure is. If it's high (above 140/90), talk to your provider about ways to get your numbers down.

Less Common Health Conditions

In addition to the common conditions listed above, some less common conditions can also cause headaches. Contact your healthcare provider if you are concerned that you are experiencing any of these conditions:

  • Glaucoma: A group of diseases affecting the optic nerve in the retina of the eye, glaucoma causes gradual vision loss. Damage occurs as fluid builds up inside the eye, increasing pressure. Headache on one side of the face can occur behind an affected eye.
  • Infections: Although rare, bacterial and viral infections affecting the head can also lead to severe, unilateral head pain. Particularly, meningitis (an infection of the tissues surrounding the brain), and encephalitis (in which the brain is inflamed) can cause debilitating headaches, among other severe symptoms.
  • Stroke: A stroke is when the blood supply to the brain gets disrupted or when a vessel in the brain bursts. This causes blood to pool in areas around the brain cells, cutting off the oxygen supply. Stroke is a medical emergency. If you experience signs of a stroke or see them in someone else, get help immediately.


Headaches can also be an unintended side effect of some medications, so it’s important to understand what you’re taking. Headaches may arise when you take:

Generally, the headaches go away if you stop or reduce intake of these drugs. However, be sure to talk to your healthcare provider first before making any changes.

Medication Overuse Headache

People who take too many pain medications too frequently—more than three times a week—can experience medication overuse headache (MOH), also known as “rebound headache.” This type is chronic, with symptoms arising daily. Several classes of drugs can cause MOHs, including:

  • Analgesic drugs, such as nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin and Advil or Motrin (ibuprofen)
  • Pain relievers combined with caffeine
  • Triptans and ergotamine, prescribed for migraine
  • Opioids, including the strong pain relievers oxycodone, hydrocodone, morphine, and others
  • Caffeine overuse from drinking too much coffee or other caffeinated beverages

Neurological Causes

Left-sided headaches can also arise due to nerve damage in the spine, neck, and head. This is the case with occipital neuralgia, giant cell arteritis, and trigeminal neuralgia. These conditions can be debilitating and require medical attention.

  • Occipital neuralgia: Occipital neuralgia is a rare and debilitating kind of headache that generally affects one side of the head. Caused by compression to the nerves, it results in very sharp, throbbing, shock-like pain in the neck, behind the ears, or back of the head. This pain tends to arise in the neck, before moving to the scalp and behind the eyes.
  • Giant cell arteritis: This is an inflammation of the temporal artery on the side of your forehead, also leads to left-sided (or unilateral) headaches. Because it can disrupt blood flow, this condition can become serious. It also causes jaw pain, loss of vision, fever, and fatigue, among other symptoms.
  • Trigeminal neuralgia: This is a chronic pain condition that occurs due to damage to the trigeminal nerve, a large three-branched nerve in the head. This can result from compression of blood vessels, as a result of multiple sclerosis, or from stroke or head trauma, among other conditions. With trigeminal neuralgia, the headache pain can range from sudden and stabbing to a more consistent aching and burning.  

Types of Headaches


Tension headaches are the most common kind. As the name suggests, they are due to both physical and psychological tension and distress. Common causes of tension headaches include:

  • Jaw clenching
  • Skipping meals
  • Overwork or overexertion
  • Depression
  • Anxiety
  • Insufficient sleep

This type of headache is usually mild to moderate in intensity, and usually affects both sides of the head, though it can affect only one side, too. Alongside pain, you may feel pressure on the face or neck.


Migraine is a primary headache disorder that can cause unilateral head pain, among other symptoms. Lasting anywhere from four to 72 hours, these moderate to severe headaches are sharp and stabbing, and localized in one area. In addition, migraine attacks cause a range of other symptoms:

  • Nausea and vomiting
  • Sensitivity to light and sound
  • Restlessness
  • Fatigue
  • Visual disturbances (auras), such as seeing zigzag patterns or flashing lights   

Migraine Variability

There are several kinds of migraines. Some, like vestibular migraine (involving visual auras, sensitivity, and extreme dizziness) arise with or without headache, while others may cause headaches on both sides. Symptoms vary considerably from person to person.


Rare and very severe, cluster headaches are characterized by recurring groupings of headache attacks (clusters) lasting one to three hours. The symptoms include:

  • Rapid onset of pain on one side of the head, usually behind one eye
  • Full intensity of pain occurs within 10–15 minutes
  • Agitation and restlessness
  • Redness or watering in the eyes
  • Nasal congestion
  • Sweating on the forehead
  • Drooping and swelling at the eyelids

During active periods, these can arise daily or even multiple times a day; however, there generally are periods of remission afterward, lasting months to years.


In some cases, headaches arise regularly and are resistant to treatment. Encompassing a couple of different types of headaches, chronic daily headache (CDH) is a term for when symptoms arise 15 or more days a month. There are several types:

These can be very difficult to live with. If you’re struggling with regular headaches, be sure to seek out medical help.


The treatment for headaches depends a great deal on the specific cause. Therapies for these conditions tend to be multifaceted, blending medical approaches with lifestyle changes. Approaches include using “rescue” medications after the onset of headache, preventive drugs, lifestyle changes, and other medical treatments.

Rescue Medications

Both over-the-counter and prescription medications help with headaches. These can come in the form of pills, or, for quicker delivery, as nasal sprays. Effective classes of drugs include:

Preventive Medications

Effective for conditions like migraine and cluster headache that are occurring more often are preventive medications. These include:

Botox Injections for Chronic Headache

In difficult-to-manage and chronic headache cases, a pain specialist may consider injection of OnabotulinumtoxinA to the nerves, or Botox injection. This prevents attacks by deadening nerves associated with pain messaging. The effect isn’t permanent, however, and additional treatment is needed every three months.

Medical Procedures for Chronic Headache

In cases of chronic headache that’s resistant to treatment, neurologists and pain specialists may consider neurostimulation to take on the pain. These focus on using mild electrical shocks or magnetic waves to stimulate nerves associated with the headaches. This essentially scrambles the pain sensation at its source. These therapies include:

  • Trigeminal nerve stimulation (TNS): When headaches start, you wear a device to stimulate the trigeminal nerve, which is associated with pain processing. The Cefaly device is a popular TNS option.
  • Single-pulse transcranial magnetic stimulation (sTMS): Another means of managing headaches after onset is transcranial magnetic stimulation. Sold under the name eNeura, it’s only available with a prescription.
  • Vagal nerve stimulation: Devices can also be used to stimulate the vagus nerve in the neck. Studies have found these to help prevent migraines and cluster headaches.  
  • Sphenopalatine ganglion stimulation: The sphenopalatine ganglion (SPG) is a bundle of nerves behind a bony structure in the nose, which is associated with facial sensation. Electrical signals to stimulate the SPG come from a small device implanted in the area through the mouth. This approach may be effective for cluster headaches.
  • Occipital nerve stimulation (ONS): Neurostimulation targeting the occipital nerve at the back of the head can also help. Devices that deliver electricity through the skin using a device or a remote-controlled implant can be considered.


Alongside medications and medical approaches are a number of things you can do on your own to help prevent and minimize headache attacks. These include:

  • Diet: Adopt a healthy, well-balanced diet and don't skip meals.  
  • Trigger control: Track the foods, drinks, and other factors that set off your migraine or cluster headaches. Work to avoid these.
  • Exercise: Staying physically active and making sure you get enough exercise can also help prevent attacks. It helps with stress and sleep.
  • Good sleep: Keep a consistent sleeping schedule and ensure you’re getting enough rest at night (for adults, that’s seven to eight hours).
  • Relaxation techniques: Take part in meditation, yoga, or other activities that promote relaxation. Even blocking off some time to take a bath can help.
  • Biofeedback: Using a specialized device, you measure physiological markers of stress in order to learn when tension, a headache trigger, is rising. By learning to sense when problems arise, you can more proactively manage your case.
  • Personal habits: Both alcohol consumption and tobacco smoking are associated with headaches and migraines, among other health issues. See what you can do to stop these habits.

When to Seek Medical Attention

While most headaches don’t necessarily call for medical attention, it’s important to remember that the pain might be related to something more serious and dangerous.

Get emergency medical help if you in the following cases:

  • Loss of consciousness following head impact
  • Very rapid onset of headache
  • Pain is more severe than usual
  • The pain worsens over 24 hours

Other cases should prompt a call to your healthcare provider. Do so if, alongside your headache, you experience the following:

  • Fever and stiff neck
  • Memory problems, confusion, or slurred speech
  • Loss of ability to coordinate limb movements
  • Loss of balance, vertigo
  • Vision problems, such as vision loss or seeing double
  • Pain in one eye, accompanied by redness
  • Problems swallowing or chewing


Headaches on the left side of the head arise due to many reasons. They can be symptoms of illnesses, underlying health conditions, allergies, side effects of medications, concussions, or be triggered by lifestyle factors, such as lack of sleep. Stress and tension bring on tension headaches, which are the most common type. You might also experience one-sided headaches due to primary headache disorders, especially migraine and cluster headaches.

Treatment for these conditions may involve taking over-the-counter or prescription pain medications, triptans, antidepressants, and others. In addition, lifestyle modifications, such as ensuring good sleep and a healthy diet, can also help.

Frequently Asked Questions

  • Do most headaches occur on the right or left side of the head?

    Unilateral (one-sided) headaches can occur on either the left or right sides of the head. Not only that, the sides are affected at equal rates. Important in identifying the type of headache is whether it affects only one side or both (bilateral).

  • How long does it typically take for a headache to go away?

    There’s no set amount of time that a headache goes away. Very much depends on the specific type it is, as well as whether other health conditions are impacting it. Migraines last anywhere from four to 72 hours, whereas other typical, tension headaches range from 20 minutes to two hours. That said, medications and other means can help resolve the issue quicker.

  • Are one-sided headaches a cause for concern?

    On their own, one-sided headaches aren’t necessarily a cause for alarm, though worth talking to your healthcare provider about. If they’re persistent, debilitating, and are coupled with vision problems, motor issues, memories, fever or stiff neck, and memory problems, then you should get help.

18 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Mark Gurarie
Mark Gurarie is a freelance writer, editor, and adjunct lecturer of writing composition at George Washington University.