Headaches on the left side of the head are commonly caused by direct blows to the head and other mild injuries, however they can also be caused by ear infections, tooth infections or migraines. This type of headache may be accompanied by other symptoms like local swelling, nausea or fever.

Although headaches on the left side of the head are not always a concerning finding, left-sided headaches that appear with symptoms like weakness on one side of the body, vision loss or seizures may be a sign of a more serious condition, like a brain tumor or serious brain injury. In these cases, imaging tests, like a CT or MRI, may be ordered.

If your headaches on the left side occur frequently, you should consult your doctor for further assessment to rule out any serious conditions and to start treatment as necessary.

Why do I have pain on the left side of my head?

Headaches on the left side of the head can be caused by:

1. Blows and injuries

A headache on the left side of the head can occur due to blows and injuries that occur in the area from an accident, like a fall, a ball to the head or a car accident. With very mild blows, other symptoms do not tend to emerge, other than some pain and mild swelling, which resolves within a few days.

However, a more significant head injury on the left side of the head can cause a concussion. Read more about the symptoms of a concussion and how it can present.

How to treat: This type of headache tends to improve within a few days. However, if the pain is intense or persists for more than a week, you should see a doctor, who may recommend analgesics like acetaminophen.

If you also experience symptoms like vomiting, seizures or loss of consciousness immediately after the injury, you should proceed to an emergency room for a more thorough assessment to rule out a serious brain injury.

2. Migraine

A migraine can cause a left side headache. It is usually described as a throbbing pain that is accompanied by other symptoms like nausea, vomiting, and sensitivity to lights or noises.

Generally, migraine pain worsens with physical activity, like walking or going up stairs. It can emerge with other symptoms like blurry vision and light flashes, which can occur before or during the headache. Learn more about migraine symptoms and how they can present.

How to treat: If you experience a migraine, you should see a doctor or neurologist for evaluation and treatment as necessary. Treatment may involve medications, like analgesics and anticonvulsants, and lifestyle changes, like sleeping, ensuring adequate sleep routines and regular exercise. A migraine diet may also be beneficial for reducing symptoms and preventing flare-ups.

3. CNS vasculitis

Headaches on the left side of the head can be caused by vasculitis, or specifically CNS vasculitis, which is characterized by swelling of arteries and veins in the brain and spine. Generally speaking, these blood vessels are protected by the blood-brain barrier, however swelling can occur if the immune system is activated to protect these vessels from a foreign antigen.

The antigen causing swelling is not easily identifiable or well-understood. It is hypothesized the CNS vasculitis may be triggered by an allergic drug reaction or by severe cocaine abuse. Symptoms of this type of vasculitis include suddenly new headaches, vision loss, memory problems, loss of balance and seizures.

How to treat: These symptoms should be assessed urgently in a hospital setting. Doctors will likely order an MRI, CT scan and/or angiogram to visualize the blood vessels and guide treatment and prevent further complications like brain ischemia and stroke. Treatment involves the administration of high-dose corticosteroids to reduce swelling.

4. Ear infection

An ear infection on the left side may cause a headache in this area. Other possible symptoms include fever and ear discharge.

How to treat: You are advised to consult a family doctor or ENT specialist if you suspect you have an ear infection. Treatment usually involves the use of medications like antibiotics and analgesics. Check-out other ways you can relieve ear pain at home.

5. Tooth infection

When tooth infections occur on the left side of the mouth, pain can radiate to the areas around the affected teeth and to the head.

Pain usually worsens when touching the affected tooth or with drinking hot or cold drink. Other common symptoms include swollen gums, easy bleeding and, in more severe cases, fever.

How to treat: If you think you may have a tooth infection, you should see your dentist for assessment and treatment as necessary. Depending on the severity, treatment may involve the use of antibiotics or even the extraction of the affected tooth. In the meantime, learn about how you can relief tooth pain at home.

6. Temporal arteritis

Temporal arteritis is an inflammation of the blood vessels. When vessels on the left side of the head are affected, it can cause symptoms like a left side headache, transient vision loss and difficulty chewing.

This pain tends to worsen with palpation, which can make common tasks like brushing you hair or sleeping on that side more difficulty. Other symptoms may include fever and general malaise.

How to treat: If you suspect you may have temporal arteritis, you should see a rheumatologist for assessment. If confirmed, treatment with medications (like oral corticosteroids) can be used to manage headache and prevent worsening.

7. Temporomandibular joint (TMJ) disorder

TMJ disorder is characterized by abnormality in the functioning of the jaw joint, which can affect jaw movements and cause significant pain. TMJ disorder that affects the left side of the face can cause pain that radiates the left ear, temple and left side of the head. This pain is commonly felt when moving the jaw from speaking, eating or drinking.

How to treat: If you suspect you may have a left-sided headache caused by TMJ on the left side of the face, you should see a dentist or orthopedic surgeon. Many times, this condition can be managed with analgesic medication, and physiotherapy, while more serious cases may require surgery. Read more about TMJ treatment options that your doctor may consider.

8. Glaucoma

Glaucoma that develops in the left eye can sometimes cause sudden pain on the left side of the head, especially in the area of the affected eye. Along with a left-sided headache, this condition can also lead to symptoms like redness in the eye, blurred vision, nausea and vomiting.

How to treat: You are advised to consult an ophthalmologist if you suspect you may have glaucoma. Treatment is aimed at preventing vision loss, and may involve the application of eye drops to reduce pressure in the eye and even surgery.

9. Tumors

Although they are rare, brain tumors can also cause left side headaches in some cases. Other symptoms will usually emerge, like seizures, weakness in certain areas of the body, nausea, vomiting and episodes of temporary vision loss. Check out the brain tumor symptoms that can occur on the left side of the brain.

The pain tends to be worse in the morning, and when lying down, coughing or with exerting force. Learn more about general cancer symptoms that you shouldn’t ignore.

How to treat: If you suspect a brain tumor, you should see your doctor for thorough imaging tests, like CT and MRI. If confirmed, the headache will generally improve when the tumor is treated. Treatment may include surgery and chemotherapy.

When to see the doctor

You should consult a doctor if you experience any of the following:

Frequent headaches with no past history or obvious cause
Weakness in a certain area of the body
Seizures
Fainting
Vision loss, even if temporary
Double vision
Cancer history
Headaches that worsen over time
Worsening of headache with lying down or coughing
Waking up at night from headaches

In these cases, tests like MRIs or CTs may be ordered to rule out serious conditions, like brain tumors. Results will typically guide treatment, which will be determined by the doctor.