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Does soap and water kill sperm following masturbation? #111/10

This question received from a woman we will can Jane) I know this is a silly question, but does soap and water kill sperm following masturbation?

I came across the following site on the Ob/Gyn site (http://forums.obgyn.net/pregnancy-birth/P-B.0205/1024.html), which stated an answer which I think clearly is wrong, but I would like confirmation of that. Look forward to hearing from you:

“If a man has had semen on his hand (but then washes it thoroughly with soap and water and then dried off his hands), is it possible for him to impregnate a female if he touches and goes into her vagina?  So basically the question is: does soap and water effectively remove all sperm from the area to which it is applied?”

“I don’t know but sperm out in the open (like on his hand) probably doesn’t live long.  If, for instance, he ejaculates into his hand and then washes his hands, then touches/penetrates a woman’s vagina, I would say he should be very careful.”


Your question Jane is not a silly question at all.

Detergents are spermicidal (kill sperm).  However, not all soaps are detergents.  Washing well with soap and water is, of course, desirable if he is going to place his finger(s) into a woman’s vagina!  


His reply on 1-19: “Thank you doctor for advising that washing with soap and water kills sperm.  This is reassuring, especially after finding that odd answer on the ObGyn website.”

Her reply on 1-26: “Hi doctor, your answer posted was different from the email reply you sent directly to me.  You added a further line indicating that not all soaps are detergents.  What do you mean by this?  Your clarification would be appreciated.”


There are thousands of detergents and they fit into several categories.  Suffice it to say, many soaps used to wash may have detergent effects, others will not. In any case, soap and water should not be considered good contraceptive. This is the best I can do for you


Detergents and Surfactants


Synthetic detergents have similar molecular structures and properties as soap. Although the cleansing action is similar, the detergents do not react as readily with hard water ions of calcium and magnesium. There are over a thousand synthetic detergents available in the United States. Detergent molecular structures consist of a long hydrocarbon chain and a water soluble ionic group. Most detergents have a negative ionic group and are called anionic detergents. The majority are alky sulfates. Others are "surfactants" (from surface active agents) which are generally known as alkyl benzene suffocates.

Cationic Detergents:

Another class of detergents have a positive ionic charge and are called "cationic" detergents. In addition to being good cleansing agents, they also possess germicidal properties which makes them useful in hospitals. Most of these detergents are derivatives of ammonia.

A cationic detergent is most likely to be found in a shampoo or clothes "rinse". The purpose is to neutralize the static electrical charges from residual anionic (negative ions) detergent molecules. Since the negative charges repel each other, the positive cationic detergent neutralizes this charge.

It may be surprising that it even works because the ammonium (+1) nitrogen is buried under the methyl groups as can be seen in the space filling model.

Neutral or non-ionic detergents:

Nonionic detergents are used in dish washing liquids. Since the detergent does not have any ionic groups, it does not react with hard water ions. In addition, nonionic detergents foam less than ionic detergents. The detergent molecules must have some polar parts to provide the necessary water solubility.  In the graphic the polar part of the molecule consists of three alcohol groups and an ester group. The non-polar part is the usual long hydrocarbon chain.

Bile Salts - Intestinal Natural Detergents:

Bile acids are produced in the liver and secreted in the intestine via the gall bladder. Bile acids are oxidation products of cholesterol. First the cholesterol is converted to the trihydroxy derivative containing three alcohol groups. The end of the alkane chain at C # 17 is converted into an acid, and finally the amino acid, glycine is bonded through an amide bond. The acid group on the glycine is converted to a salt. The bile salt is called sodiumglycoholate. Another salt can be made with a chemical called taurine.

The main function of bile salts is to act as a soap or detergent in the digestive processes. The major action of a bile salt is to emulsify fats and oils into smaller droplets. The various enzymes can then break down the fats and oils. 


Key words:  soap, water, kill sperm, confirmation, semen, hands, impregnate, ejaculates, penetrates, vagina, detergents, spermicides

Posted 1-26-2010, Updated 1-27-2010, Updated 2-1-2010 

Robert A. Hatcher MD, MPH
Emeritus Professor of Gynecology and Obstetrics
Emory University School of Medicine
Atlanta, GA

The directors and owners of this website and any publications and information concerning health matters offered here advise a person with a particular problem to consult a primary-care clinician or a specialist in obstetrics, gynecology, or urology (depending on the problem or the contraceptive) as well as the product package insert and other references before diagnosing, managing, or treating the problem.
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