Vaginal lubrication is a naturally produced fluid that lubricates a woman's vagina. Vaginal lubrication is always present, but production increases significantly near ovulation and during sexual arousal in anticipation of sexual intercourse. Vaginal dryness is the condition in which this lubrication is insufficient, and sometimes artificial lubricants are used to augment it. Without sufficient lubrication, sexual intercourse can be painful. The vaginal lining has no glands, and therefore the vagina must rely on other methods of lubrication. Plasma from vaginal walls due to vascular engorgement is considered to be the chief lubrication source, and the Bartholin's glands , located slightly below and to the left and right of the introitus vaginal opening , also secrete mucus to augment vaginal-wall secretions.