This beloved cure-all of Czech grandmothers is derived from mineral water bottled in the Luhačovice spa region. While the makers of the product tout its carbon dioxide content, as well as the salts contained therein, as helpful for dissolving mucus when sipped or flushed through the nasal cavities, in general, a simple salt-water gargle can help relieve a sore throat, too. Excessive sodium, however, has been found to cause high blood pressure so use in moderation.