Viral Pharyngitis: This is the most common cause of sore throat in adolescents, often accompanied by nausea, vomiting, and headache due to the body's inflammatory response to the virus.

Strep Throat (Streptococcal Pharyngitis): Caused by Group A beta-hemolytic streptococcus, it presents with sore throat, fever, and can be accompanied by nausea and vomiting. It's a common bacterial infection in this age group.
Influenza: Especially during flu season, influenza can cause a sore throat, headache, nausea, and vomiting, among other symptoms like fever and body aches.
Mononucleosis (Mono): Caused by the Epstein-Barr virus, it can present with sore throat, fever, headache, and sometimes nausea and vomiting, particularly in adolescents.

Meningitis: Although less common, meningitis is a serious and potentially life-threatening condition that can present with headache, nausea, vomiting, and sometimes sore throat. It requires immediate medical attention.
Encephalitis: An inflammation of the brain, usually caused by viral infections, which can present with headache, fever, confusion, and sometimes sore throat and nausea.
Lemierre's Syndrome: A rare but serious condition that starts with a sore throat and can progress to include symptoms like headache and nausea, due to a bacterial infection that spreads to the jugular vein.

Rheumatic Fever: A complication of untreated strep throat, it can occur weeks after the initial infection and presents with a variety of symptoms including joint pain, fever, and sometimes headache and nausea.
Tonsillar Abscess: A collection of pus behind the tonsils, which can cause severe sore throat, difficulty swallowing, fever, and sometimes nausea and vomiting.
Peritonsillar Abscess: Similar to a tonsillar abscess but located next to the tonsils, it can cause severe throat pain, fever, and sometimes nausea and vomiting.