Besides unattractive aesthetic effect lip fever causes a lot of discomfort. If it spread out of lip lines it may look ugly. But I have some advice on how to conceal it.
Use tonal cream. First apply some anti-herpes cream on the affected spots and than apply some correcting pencil to red area. Thus tonal cream and face powder will evenly cover the skin.

Try not to overdo with make up because it may cause itching and may soil the skin pores.