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The cause of respiratory infections can either be a viral or due to bacterial origin. Most Viral infections or the upper respiratory tract are usually benign, and subside within 7 to 10 days with conservative management with anti-inflammatory medications like advil or motrin. Cough and throat irritation can be reduced with cough lozenges and vitamin C supplements.
Ban lan gen is marketed as a herbal tea, to cure sorethroats, and infections. But its efficacy and actual usefulness is not been scientifically proved.
In case of severe symptoms, you may need to seek a doctors help, for prescription of antibiotics to treat infections, and to rule out any predisposing conditions.