In Dark Souls III you don't start hollowing until you ask Yoel of Londo to "draw your true strength", which in practice gives you up to 5 free levels at the cost of getting hollowing points each time you die, which change your appearance.
To reverse this process, you need to pay a lot of souls... however, apparently you NEED to get hollow to get the best ending.
Where is the catch?
Hollowing in Dark Souls III doesn't have any downsides besides appearance—even then, you can appear normal with the Untrue Dark Ring.
You're safe to stay Hollowed if you so wish. It won't come with any cons besides affecting your skin.
As an extra fact, the Hollowed infusion can only be wielded while Hollowed. This gives your infused item a scaling with luck as well as an inherent boost in your luck stat.
