One of the most common causes of white lumps appearing inside the throat is tonsillitis. Other causes may include candidiasis, herpes, oral thrush, mononucleosis, strep throat and leukoplakia.
White, pus-filled lumps on the tonsils and the back of the throat are a common occurrence in tonsillitis. According to WebMD, to determine the cause of the white bumps, a doctor may perform a throat swab culture or a strep test. The doctor may prescribe a course of antibiotics to cure a bacterial infection. The symptoms usually get better in 3 or 4 days after the start of the treatment. Other common symptoms of tonsillitis include pain in the ears, coughing and headaches.