What's the cause of having pus in the vagina?

Infection: Same as anywhere else, it suggests the presence of an infection. Particularly if there has been a change in color/consistency / odor / quantity--you should be checked by your gyn or primary if covers gyn, or can go to county public health ("std") clinic for exam, testing and appropriate treatment.

If Pus, Infection: Pus is an accumulation of white blood cells gathering to fight and eat bacteria. If greenish, this color from enzymes which wbcs produce internally after eating bacteria & in process of killing and digesting the bacteria, as food, if able. If in vagina, not associated with very recent intercourse, suspect std, esp. Gonorrhea; if not txed & wiped out, can lead to many problems, including sterility.

Infection: Not normal. Get tested for stds right away.