The antiviral treatment is most effective when you take it within the first five days of symptoms appearing. You can ease your symptoms by: keeping the affected area clean using plain or salt water to prevent blisters or ulcers from becoming infected applying petroleum jelly, such as Vaseline, to any blisters or ulcers to reduce the pain when passing urine asking a healthcare provider to recommend painkilling creams avoiding tight clothing because it may irritate the blisters and ulcers.