Vaginal lubrication is a lubricating fluid that is naturally produced in a woman's vagina. Vaginal lubrication or moistness is always present, but production increases significantly 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 both to the woman and the man. The vagina has no glands, and therefore must rely on other methods of lubrication. Plasma seepage 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 (opening of the vagina), also secrete mucus to augment vaginal-wall secretions.
The lubricative fluid contains water, pyridine, squalene, urea, acetic acid, lactic acid, complex alcohols and glycols, ketones, and aldehydes. It can vary in consistency, texture, taste, color, and odor, depending on sexual arousal, the phase of the menstrual cycle, the presence of an infection, certain drugs, genetic factors, and diet.
Vaginal fluid is slightly acidic and can become more acidic with certain sexually transmitted diseases. The normal pH of vaginal fluid is between 3.8 and 4.5, whereas male semen is typically between 7.2 and 8.0 (a neutral substance has a pH of 7.0).
The human vagina is innervated by nerves that respond to vasoactive intestinal polypeptide (VIP). As a consequence, VIP induces an increase in vaginal blood flow accompanied by an increase in vaginal lubrication. The findings suggest that VIP may participate in the control of the local physiological changes observed during sexual arousal: genital vasodilation and increase in vaginal lubrication.
Vaginal dryness 
Insufficient lubrication or vaginal dryness in women can cause dyspareunia, which is a type of sexual pain disorder. While vaginal dryness is considered an indicator for sexual arousal disorder, male circumcision exacerbates female vaginal dryness during intercourse. Vaginal dryness may also result from insufficient excitement and stimulation or from hormonal changes caused by menopause (potentially causing atrophic vaginitis), pregnancy, or breast-feeding. Irritation from contraceptive creams and foams can also cause dryness, as can fear and anxiety about sexual intimacy.
Certain medications, including some over-the-counter antihistamines, as well as life events such as pregnancy, lactation, menopause, aging or diseases such as diabetes, will inhibit lubrication. Medicines with anticholinergic or sympathomimetic effects will dry out the mucosal or "wet" tissues of the vagina. Such medicines include many common drugs for allergic, cardiovascular, psychiatric, and other medical conditions. Oral contraceptives may also increase or decrease vaginal lubrication.
Artificial lubricants 
When a woman is experiencing vaginal dryness before sexual activity, during which she produces insufficient vaginal lubrication, sexual intercourse may be uncomfortable or painful for her. A personal lubricant can be applied to the vaginal opening, the penis, or both, to augment the naturally produced lubrication and prevent or reduce the discomfort or pain. More rarely, a vaginal suppository may be inserted prior to intercourse.
Oil-based lubricants can weaken latex and reduce the effectiveness of condoms, latex gloves, or dental dams as either forms of birth control or for protection from sexually transmitted diseases, so water- or silicone-based lubricants are often used instead. The use of an artificial lubricant can make sexual intercourse less painful for a woman, but does not address the underlying cause of the vaginal dryness itself.
Dry sex 
Some women practice dry sex. This involves the woman having sexual intercourse after removing vaginal lubrication in some way. The rationale for the practice seems to be for cleansing purposes and to enhance the sexual pleasure of the male. However, besides making sexual intercourse painful for the female and the male, the practice is believed to increase the risk of transmitting sexually transmitted diseases for both partners. For instance, the risk of HIV transmission is increased by lacerations in the vaginal tissue resulting from the lack of lubrication.
See also 
- Toxic shock syndrome, linked to the use of tampons which excessively dry up the vaginal lubrication
- Spinnbarkeit, the stretchiness of cervical mucus associated with ovulation; one property of this secretion is to lubricate the vagina
- Urethral sponge
- Skene's gland
- Bartholin's gland
- AFE zone
- Female ejaculation
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- Local voices: What some Harare men say about preparation for sex
- Concern voiced over "dry sex" practices in South Africa
- “Dry sex” worsens AIDS numbers in southern Africa - Salon.com
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