Fenistil Cold Sore Cream Fenistil Cold Sore Cream is used for the treatment of herpes simplex virus infections of the lips & face (herpes labialis). Ingredients The active ingredient is Penciclovir (10mg/g). The other ingredients are White Soft Paraffin, Liquid Paraffin, Cetostearyl Alcohol, Propylene Glycol, Cetomacrogol 1000 & Purified Water. Directions Adults (including the elderly) & children over 12 years of age: Fenistil Cold Sore Cream should be applied at Approx. two hourly intervals during waking hours, (approximately 8 times a day). Treatment should be continued for 4 days. If the condition gets worse or does not improve after 4 days treatment, seek medical advice. Treatment should be started as early as possible after the first sign of an infection. Children (under 12 years): No work has been carried out in children below 12 years of age.