Levomenthol, Squill Tincture, Liquorice Liquid Extract Chesty cough mixture mentholated relieves the symptoms of chesty coughs and sore throats. Covonia Chesty Cough Mixture Mentholated contains liquorice and squill which belong to a group of medicines known as expectorants. They help remove phlegm in people with chesty coughs. Menthol helps relieve congestion in chesty coughs and bronchitis.