Personal lubricants (colloquially termed lube) are specialized lubricants used during human sexual activity to reduce friction between body parts, or between body parts and other objects. They are used during sexual acts such as intercourse and masturbation, to reduce friction to or between the penis, vagina, armpit, anus, or other body parts, or applied to sex toys to reduce friction or ease in penetration. Surgical or medical lubricants or gels, which are similar but not usually referred to or labelled as "personal" lubricants, may be used for medical purposes such as speculum insertion or introduction of a catheter.
Personal lubricant types 
Water-based personal lubricants are water-soluble and are the most widely-used personal lubricants. The earliest water-based lubricants were cellulose ether or glycerin solutions. Products available today may have various agents added for even dispersal, moisture retention, and resistance to contamination. The viscosity of these products can be altered by adjusting their water content and concentration of cellulose or other gel-forming hydrophilic ingredient.
Because water-based personal lubricants absorb into the skin and evaporate, most water-based lubricants have a tendency to dry out during use, but reapplication of the lubricant or application of water or saliva is usually sufficient to reactivate them. When the lubricant eventually dries out, it may leave behind a residue derived from the other ingredients in the formulation. This may require reapplication during sex, and/or removal of the residue with water. Some newer water-based lubricants are formulated with natural skin moisturizers, such as carrageenan, and may not leave a sticky residue after evaporation. Carrageenan has also been shown to be a potent inhibitor of human papillomavirus infection. Carraguard, an aqueous gel containing carrageenan developed as a microbicide, has been shown in some preliminary studies to inhibit HIV transmission, although results have been mixed. Scientists are testing whether anti-retroviral lubricants or gels can be applied to aid in the prevention of transmission of HIV.
Typical water-based lubricants may be incompatible with sex acts that occur in water (such as in a bathtub, pool, or hot tub) as they can be dissolved or dispersed in water.
A 2011 study by the Population Council found that many commercially-available water-based sexual lubricants tested damaged human rectal cells and that some of them - those containing polyquaternium-15 - appeared to actively increase HIV replication in cell cultures and therefore could raise one's risk of HIV transmission. Water-based ‘lubes’ have been recommended for use in safer sex because they do not weaken condoms like oil-based lubricants do. The researchers concluded: "Since it is the condom that is protecting users from HIV rather than the lube, condom users should still be encouraged to use water-based lubes because condoms are also more likely to break, and trauma to the rectal lining occur, with no lube". They also cited silicone-based lubricants as a potential alternative, although they did not test any silicone lubes in their study. Lubricants and creams containing the spermicide nonoxynol-9 are known to be cytotoxic, as studies have shown the compound damages cells and makes users more vulnerable to HIV.
Oil-based lubricants, for example petroleum-based lubricants (such as petroleum jelly), can increase the likelihood of breakage and slipping of latex condoms due to loss of elasticity caused by these lubricants. Oil may also create tiny holes in the latex. Oil-based lubricants may be considered desirable for people who are in relationships not requiring condom use and who wish to avoid certain additives and preservatives often found in other lubricants.
Fertility lubricants 
Fertility lubricants, also known as 'sperm-friendly' lubricants, are specifically formulated to be safe for use by couples who are trying to conceive. Fertility lubricants are pH-balanced and designed not to affect the body's electrolyte balance. They have a specific osmolality range that is safe for sperm. In addition to having the correct pH and osmolality range, fertility lubricants should be free of chemicals that can potentially harm sperm. Fertility lubricants are non-spermicidal and do not harm viability or motility of human sperm.
One fertility lubricant has a patented formula that contains calcium (Ca2+) and magnesium (Mg2+) ions and has an optimal pH and osmolality range to better mimic the natural fertile cervical fluids to alleviate the problem of vaginal dryness and to assist couples trying to conceive a baby naturally. The ASRM has published clinical data on this fertility lubricant that contains calcium and magnesium as safe for sperm motility, sperm viability and embryo development.
For couples trying to conceive, it is important to choose a lubricant carefully. Most personal lubricants, including saliva, olive oil, or water[clarification needed], may potentially damage sperm and keep them from swimming normally, and therefore are not recommended for use if pregnancy is the objective.
Organic or natural 
In the United States, the first certified organic personal lubricant labeled with the USDA organic seal was Nude Personal Lubricant, which was created in 2004 by Applied Organics. The US Food and Drug Administration (FDA) regulates lubricant as a medical device rather than as a cosmetic. Because of strict FDA guidelines for medical devices, organic personal lubricants were no longer allowed to carry a USDA seal for Nude Personal Lubricant, and that it should be very careful about using the term organic anywhere on its label. Many of these types of lubricants also market themselves as "natural" and do not contain paraben, glycerin, DEA or animal-based ingredients. Some contain botanicals such as aloe vera or plant extracts.
ANSI and NSF have partnered with organic certifiers around the country in order to provide a definitive set of compliance guidelines for organic lubricants and other personal care products. NSF/ANSI 305 organic standards for body care are modeled off of the USDA organic standards for foods. Their certification process calls for transparency in the ingredients used and the processes utilized to turn those ingredients into finished products.
In December of 2011, Aloe Cadabra, manufactured by Seven Oaks Farms in Ventura, California, became the first personal lubricant certified to the new NSF/ANSI 305 Organic Body Care Standards.
Silicone-based lubricants are usually formulated with fewer than four ingredients and do not contain any water. Silicone lubricants offer a different feel from water-based personal lubricants. Silicone-based lubricants are not absorbed by skin or mucus membranes, and consequently last longer than water-based lubricants. Many different silicone lubricants are commercially available with varying quality and performance. Not all silicone-based lubricants are certified latex-safe, but silicone-based lubricants have not been shown to increase the risk of HIV transmission during anal intercourse, as some water-based lubes have.
Silicone-based lubricants are not usually recommended for use with sex toys or other products that are made from silicone because the formula may dissolve the surface making it sticky to the touch, and cause disintegration of the item over time. This damage may create a breeding ground for bacteria. In most cases a warning is listed on the product label. At least one manufacturer claims their silicone-based lubricant is safe for use with silicone products. Silicone-based lubricant is also used in the manufacture of pre-lubricated condoms, due to its long-lasting properties and superior latex compatibility.
Specialty lubricants 
Warming lubricants contain specific ingredients to cause a sensation of warmth. Breathing on these types of lubricants may increase the effect. "Cooling" or "tingling" lubricants may contain ingredients such as peppermint. Some lubricants are sold together, such as "hot and cold", or are marketed for a specific use or effect. Flavored lubricants contain flavorings, such as fruit flavors, to enhance oral contact. "Edible" lubricants may be flavored and/or may not contain any ingredients that are not advisable to eat.
Many lubricants are safe for anal sex, but there are products that are specifically marketed or designed to enhance enjoyment of anal sex. Often, this is simply a thicker gel rather than a liquid. This thicker consistency is preferable because it helps the lubricant stay in place. Some lubricants contain benzocaine, an anesthetic. However, the use of any numbing agent for anal penetration is not recommended as a lack of sensation makes accidental injury more likely. In addition, benzocaine can cause an allergic reaction in those with an allergy to PABA (4-Aminobenzoic acid). Some lubricants are conveniently packaged for ease of application. Many of these products such as Astroglide Shooters have been pulled from the market recently[when?] due to FDA Medical Device Requirements. Products containing benzocaine can numb all body parts with which they come in contact.
Other products that have been used as personal lubricants include vegetable shortening, which is durable and inexpensive but damaging to latex. In a controversial scene in the movie Last Tango in Paris, the character Paul, played by Marlon Brando, uses butter during anal sex with the character Jeanne played by Maria Schneider.
Sexual activity 
A personal lubricant can be used to increase pleasure and reduce pain during sexual intercourse or other activities and may be used for lubricating the penis, vagina, anus or dildo or other sex toy before or during activity. Lubricant may be applied to any body part desired, to the inside and/or outside of condoms, or to the hands or fingers. Personal lubricants are particularly useful for intercourse when a partner experiences dryness or excessive contraction (tightness) of the vagina or anus. Anal sex generally requires more generous application of lubricant since the anus does not have natural lubrication sufficient for most sexual activity.
In medicine, lubricants can be used for gynecological examinations, digital rectal examinations, the insertion of catheters, and the use of enema nozzles and rectal thermometers. The class of lubricants now known as "personal" derives from surgical lubricants; K-Y Jelly was originally introduced in 1904 for this purpose.
While most males and females both produce varying amounts of their own lubrication, it is often desirable to add extra lubrication. There are specific lubricants which may be used in male masturbation but are not suitable for vaginal or anal use or for use with condoms. Lubricant that is safe for sexual intercourse is also safe for masturbation.
Care is recommended in choosing a personal lubricant. Some women may experience irritation from the use of certain lubricants. Some lubricants (as mentioned above under 'Water-based') have been found to damage cells or even increase the replication of the HIV virus. Nonoxynol-9, a spermicide contained in some lubricants, is an irritant and can cause micro-tears which may increase the rate of HIV transmission and HPV infection. Spermicidally lubricated condoms do not contain enough spermicide to increase contraceptive effectiveness, but application of separate spermicide is thought to reduce pregnancy rates significantly.
See also 
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