The white "stuff" at the back of the throat is most likely harmless tonsilloliths, or tonsil stones, where bacteria and other debris are trapped, according to MedGuidance. They can be removed with a toothpick or cotton swab. Painful tonsilloliths may indicate an infection requiring medical attention.
Tonsilloliths form on the surface of the tonsils, where bacteria collect and cause a bad odor, according to MedGuidance. They harden into "stones" and appear as chunks in the throat. They may cause symptoms such as swelling of the tonsils, difficulty swallowing, sore throat and earache. After removal, they may return, even with gargling and good hygiene. Tonsilloliths are associated with tonsillitis, although their actual cause is unknown.
Other causes of a white substance in the throat may include post-nasal drip resulting from a sinus infection, causing a whitish or yellowish mucus in the throat, according to MedGuidance. Another possibility is a peritonsillar abscess, resulting from an untreated or partially treated case of tonsillitis. This may be accompanied by a fever and sore throat. Still another cause of a white throat is thrush, a painful fungal infection that appears as a cheesy substance on the tongue, tonsils and inner cheeks.
If a person has tonsillitis, gargling with warm water will help relieve the symptoms, according to MedGuidance. Antibiotics can fight the bacteria in the tonsils, but won't remove the stones. Severe cases may require removal by surgery or a tonsillectomy.