Nothing.
A thicker layer of keratin.
skin is thicker on your feet
It mostly just makes them healthier. But, the healthier they are, the faster they will grow. It will also make them thicker.
Try shampoo you can find at petco. its for horses and it makes your hair grow faster and thicker
Men generally have thicker skin than woman.
It is good for the hair but may not make it thicker it may be healthy.
Yes, they are going to help your hair grow but keep in mind you can just take a biotin supplement which is know to help skin, nail, and hair health. Plus some even say it makes their hair thicker.
Shaving does not "make your hair grow back thicker".
Thicker and longer? Never ever put moisturiser on your eye lashes this will them spilt and doesn't show a good result. But What actually makes them long and thick by just putting Vaseline on them. this will help them grow quicker and thicker.
On your back
Eat more.