It releases tension:

When you press a stress ball, the muscles in your hands and your wrists tighten up and when you release the ball it relaxes the tendons and muscles in the area.

This helps one to release tension build up due to stress. Ohhhhhh!

It stimulates your nerves:

It is a known fact that the extremities of your body, i.e., the hands and feet have nerve endings that are connected to your brain. The nerve ending in the hands are connected to the limbic region that is solely responsible for controlling your emotions. Pressing the stress ball with your palm has an effect like the acupressure, where stimulating the nerves in one area helps the other areas to function at its optimum. Ahhhhhhhhh!

It Improves muscle strength:

The squeezing enhances movement in muscles that result in the production of more nuclei. More muscle cells lead to better and bigger muscles seen through the toned muscles. Your susceptibility to injuries is decreased with the exercises.  There is also improved wrist strength when the ball is squeezed as well as finger strength through stress ball pinching activities.  Ohhhhhhhhh!

It improves your mood: When the nerves connected to your brain are stimulated by pressing a stress ball, it relieves muscular tension and also helps to secrete endorphins that minimise the cortisol levels in the blood. This helps to improve your mood as well.   Ahhhhhhhhhh!