The first medical doctor to advocate for the adoption of circumcision was the eminent English physician, Jonathan Hutchinson. In 1855, he published a study in which he compared the rate of contraction of venereal disease amongst the gentile and Jewish population of London. Although his manipulation and usage of the data has since been shown to have been flawed (the protection that Jews appear to have are more likely due to cultural factors), his study appeared to demonstrate that circumcised men were significantly less vulnerable to such disease. (A 2006 systematic review concluded that the evidence "strongly indicates that circumcised men are at lower risk of chancroid and syphilis.")
Hutchinson was a notable leader in the campaign for medical circumcision for the next fifty years, publishing A plea for circumcison in the British Medical Journal (1890), where he contended that the foreskin "... constitutes a harbour for filth, and is a constant source of irritation. It conduces to masturbation, and adds to the difficulties of sexual continence. It increases the risk of syphilis in early life, and of cancer in the aged." As can be seen, he was also a convert to the idea that circumcision would prevent masturbation, a great Victorian concern. In an 1893 article, On circumcision as a preventive of masturbation he wrote: "I am inclined to believe that [circumcision] may often accomplish much, both in breaking the habit [of masturbation] as an immediate result, and in diminishing the temptation to it subsequently."
Nathaniel Heckford, a paediatrician at the East London Hospital for Children, wrote Circumcision as a Remedial Measure in Certain Cases of Epilepsy, Chorea, etc. (1865), in which he argued that circumcision acted as an effective remedial measure in the prevention of certain cases of epilepsy and chorea.
These increasingly common medical beliefs were even applied to females. The controversial obstetrical surgeon Isaac Baker Brown founded the London Surgical Home for Women in 1858, where he worked on advancing surgical procedures. In 1866, Baker Brown described the use of clitoridectomy, the removal of the clitoris, as a cure for several conditions, including epilepsy, catalepsy and mania, which he attributed to masturbation. In On the Curability of Certain Forms of Insanity, Epilepsy, Catalepsy, and Hysteria in Females, he gave a 70 per cent success rate using this treatment.
However, during 1866, Baker Brown began to receive negative feedback from within the medical profession from doctors who opposed the use of clitoridectomies and questioned the validity of Baker Brown's claims of success. An article appeared in The Times in December, which was favourable towards Baker Brown's work but suggested that Baker Brown had treated women of unsound mind. He was also accused of performing clitoridectomies without the consent or knowledge of his patients or their families. In 1867 he was expelled from the Obstetrical Society of London for carrying out the operations without consent. Baker Brown's ideas were more accepted in the United States, where, from the 1860s, the operation was being used to cure hysteria, nymphomania, and in young girls what was called "rebellion" or "unfeminine aggression".
Lewis Sayre, New York orthopedic surgeon, became a prominent advocate for circumcision in America. In 1870, he examined a five-year-old boy who was unable to straighten his legs, and whose condition had so far defied treatment. Upon noting that the boy's genitals were inflamed, Sayre hypothesized that chronic irritation of the boy's foreskin had paralyzed his knees via reflex neurosis. Sayre circumcised the boy, and within a few weeks, he recovered from his paralysis. After several additional incidents in which circumcision also appeared effective in treating paralyzed joints, Sayre began to promote circumcision as a powerful orthopedic remedy. Sayre's prominence within the medical profession allowed him to reach a wide audience.
As more practitioners tried circumcision as a treatment for otherwise intractable medical conditions, sometimes achieving positive results, the list of ailments reputed to be treatable through circumcision grew. By the 1890s, hernia, bladder infections, kidney stones, insomnia, chronic indigestion, rheumatism, epilepsy, asthma, bedwetting, Bright's disease, erectile dysfunction, syphilis, insanity, and skin cancer had all been linked to the foreskin, and many physicians advocated universal circumcision as a preventive health measure.
Specific medical arguments aside, several hypotheses have been raised in explaining the public's acceptance of infant circumcision as preventive medicine. The success of the germ theory of disease had not only enabled physicians to combat many of the postoperative complications of surgery, but had made the wider public deeply suspicious of dirt and bodily secretions. Accordingly, the smegma that collects under the foreskin was viewed as unhealthy, and circumcision readily accepted as good penile hygiene. Secondly, moral sentiment of the day regarded masturbation as not only sinful, but also physically and mentally unhealthy, stimulating the foreskin to produce the host of maladies of which it was suspected. In this climate, circumcision could be employed as a means of discouraging masturbation. All About the Baby, a popular parenting book of the 1890s, recommended infant circumcision for precisely this purpose. (However, a survey of 1410 men in the United States in 1992, Laumann found that circumcised men were more likely to report masturbating at least once a month.) As hospitals proliferated in urban areas, childbirth, at least among the upper and middle classes, was increasingly under the care of physicians in hospitals rather than with midwives in the home. It has been suggested that once a critical mass of infants were being circumcised in the hospital, circumcision became a class marker of those wealthy enough to afford a hospital birth.
During the same time period, circumcision was becoming easier to perform. William Stewart Halsted's 1885 discovery of hypodermic cocaine as a local anaesthetic made it easier for doctors without expertise in the use of chloroform and other general anaesthetics to perform minor surgeries. Also, several mechanically aided circumcision techniques, forerunners of modern clamp-based circumcision methods, were first published in the medical literature of the 1890s, allowing surgeons to perform circumcisions more safely and successfully.
By the 1920s, advances in the understanding of disease had undermined much of the original medical basis for preventive circumcision. Doctors continued to promote it, however, as good penile hygiene and as a preventive for a handful of conditions local to the penis: balanitis, phimosis, and penile cancer.
In 2012 the American Academy of Pediatrics found that "the health benefits of newborn male circumcision outweigh the risks, but the benefits are not great enough to recommend universal newborn circumcision"
The origin of male circumcision is not known with certainty. It has been variously proposed that it began as a religious sacrifice, as a rite of passage marking a boy's entrance into adulthood, as a form of sympathetic magic to ensure virility or fertility, as a means of reducing sexual pleasure, as an aid to hygiene where regular bathing was impractical, as a means of marking those of higher social status, as a means of humiliating enemies and slaves by symbolic castration, as a means of differentiating a circumcising group from their non-circumcising neighbors, as a means of discouraging masturbation or other socially proscribed sexual behaviors, as a means of removing "excess" pleasure, as a means of increasing a man's attractiveness to women, as a demonstration of one's ability to endure pain, or as a male counterpart to menstruation or the breaking of the hymen, or to copy the rare natural occurrence of a missing foreskin of an important leader, a way to repel demonesses, and as a display of disgust of the smegma produced by the foreskin. Removing the foreskin can prevent or treat a medical condition known as phimosis. It has been suggested that the custom of circumcision gave advantages to tribes that practiced it and thus led to its spread.
Darby describes these theories as "conflicting", and states that "the only point of agreement among proponents of the various theories is that promoting good health had nothing to do with it." Immerman et al. suggest that circumcision causes lowered sexual arousal of pubescent males, and hypothesize that this was a competitive advantage to tribes practising circumcision, leading to its spread. Wilson suggests that circumcision reduces insemination efficiency, reducing a man's capacity for extra-pair fertilizations by impairing sperm competition. Thus, men who display this signal of sexual obedience may gain social benefits if married men are selected to offer social trust and investment preferentially to peers who are less threatening to their paternity. It is possible that circumcision arose independently in different cultures for different reasons.