Written by Tom Fahey
14 January 2010

Guys are sensitive about their penis size in the shower or locker room. Cold, stress or exercise can make an otherwise normal size penis retract like a turtle into its shell, which can be embarrassing and humiliating. Shrinking penis syndrome is caused by contraction of the dartos muscle (smooth muscle lying beneath the skin of the scrotum), which can make some guys look like prepubertal boys.

Egyptian researchers found that injecting 100 units of BOTOX into the dartos muscle decreased the frequency and extent of penile retraction in 70 percent of men treated with the drug. BOTOX prevented retraction of the penis, but did not increase length. The effects lasted six months. You no longer have to be embarrassed in the locker room— unless you have a small penis in the first place. (Journal Sexual Medicine, 6: 2788-2794, 2009)