Free Salonpas Gel-Patch SampleGet a Free Salonpas Gel-Patch Sample. Salonpas Gel-Patch contains l-menthol and water. When applied to the skin, water starts to evaporate creating a cooling effect. Menthol strengthens the cooling effect even further, creating a cooling sensation to help relieve pain. It works like ice, keeping the affected area cool for up to 6 hours. To recieve your FREE Salonpas Gel-Patch sample, simply fill in the form with your information. UK only.