I have a question regarding the testicle: When I rub the under of the testicle it feels good, but I also noticed that it contracts and expands too! Is this dangerous?
I am masturbating daily, is this dangerous too?
First, we need to straighten out your terms. The bag under your penis is your scrotum. Inside the scrotum are two oval shaped things which are your testicles. The drawing to the right, from the Mayo Clinic Foundation, shows a cut-away view of the penis, scrotum, and testicles.
The picture to the right illustrates a drawn up scrotum and a relaxed or expanded scrotum. The scrotum expands and contracts for two reasons. One is to regulate the temperature of the testicles. They need to be a few degrees cooler than the rest of your body in order to produce sperm. The second reason is to protect your testicles from getting banged around. Thus, when you run, the scrotum draws up to keep the testicles from being bumped by your legs. The scrotum also draws up when you reach a certain level of sexual arousal because the act of sex can also bump the testicles.
Certain areas on your body are sensitive to touch and produce sexual arousal. Underneath the scrotum is one of those areas. It is a physical response to stimulation, just as sudden bright lights make you blink or touching something hot makes you pull back quickly. So it is normal, working as it should, and is not dangerous.
In regards to masturbation, see "Can you masturbate too much?"