Some people suffering from strep throat will also get swollen lymph glands in their neck. Others experience vomiting or a red skin rash. How Long Does Strep Throat Last? Strep throat will only last 3 to 7 days with or without treatment. Doctors usually treat strep throat with antibiotics even though they will not make you well any faster. Strep throat contagiousness will continue for 24 hours once antibiotics are started. With no treatment, strep throat continues to be contagious until symptoms resolve.