While it may be considered unharmful, no act really does have positive without the negative sides, and masturbation is not left out with its risks.
1. Those who use objects as tools of masturbation risk being stuck by insertion of these objects in the vagina (for women) or any (for both genders). Wikipedia reports the case of a German woman in a hospital, who had two pencils stuck in her urinary bladder in the course of masturbation. This is just few out of other reported cases of people who had objects stucked up down there, while it has also cost few lives who couldn’t access urgent help from medical experts.
2. Decreased s€xual sensitivity
Masturbation often conditions the body to respond to a certain way of s€xual stimulation. This reduces s€xual sensitivity when patners meet as one is not able to meet up with the demands the other is used to. Worthy of note is that this has caused major crises in relationships.
3. Excessive masturbation, especially aggressive stroking in men can cause trauma or injury to the p€nis and its blood vessels, which is usually associated with severe penile pain during ejaculation.
Masturbation is addictive and many have found themselves returning to it even after making genuine commitment to quit. This has caused low self-esteem and even depression among many. Others have secluded themselves socially and withdrawn to a private life which more often than not is more dangerous.
5. Squeezing the p€nis or scrotum during ejaculation can damage blood vessels and nerves, which can result in semen entering the urinary bladder, ejaculation problems or even s€xual dysfunction.