The left side of the throat hurts when swallowing, so what kind of diseases should be alert to tonsillitis, acute pharyngitis, laryngeal foreign body, tonsil cancer and other diseases. 1. Tonsillitis: this disease is generally caused by bacterial virus and other pathogenic microorganisms infection, non-specific inflammation of tonsil, left tonsil can be swollen, congested and suppurative tissues and other pathological changes, unilateral pain in swallowing occurs. 2. Acute pharyngitis: this disease is related to bacterial and viral infection, the mucous membrane of pharynx will be congested and swollen due to inflammation, and when it occurs in the left side of pharyngeal wall, the patient will feel discomfort and pain in swallowing. 3. Tonsillar cancer: left tonsillar cancer will lead to foreign body sensation in the throat and sore throat on one side, which is usually more obvious when swallowing. The pain on the left side of the throat when swallowing difficulty may also be related to hypopharyngeal cancer, caudate overgrowth syndrome, etc. It is recommended to go to the hospital in time to find out the cause of the disease and carry out the relevant treatment.