There are three main reasons for the pain in the left ear: First, the patient may have a foreign body in the ear canal. This is often seen in children who are particularly naughty when playing and often stuff tiny substances in their ears, resulting in a pain in the ear. Second, the main consideration is the formation of boils or inflammation in the external ear canal. Patients may often dig their ears or wash their hair or take a bath, and the water inside their ears stimulates the mucous membrane of the ear canal to become congested and inflamed. Thirdly, the main consideration is neuropathic pain, such as patients who suffer from insomnia, stay up late often, or have particularly high mental stress, after which they are prone to such a condition. Regardless of which of the above causes causes the pain in the ear, it is best to go to the hospital for a detailed examination and further treatment.