Permanent marker is considered bad for your skin and it's not recommended by doctors or skin doctors etc or even the permanent marker manufacturer to write on your skin.
The permanent markers and sharpies contain toxic chemicals that make them bad for your skin and could potentially cause ink poisoning as well.
So you write on your skin with permanent marker at your own risk.
Permanent markers are toxic and do contain toxic chemicals that are both bad to breathe and bad for your skin so it's not recommended to write on your skin and you should not breathe in the sharpies or permanent markers or sniff the sharpies or permanent markers.
Drawing on your skin with permanent marker is considered bad because permanent markers and sharpies contain some toxic chemicals that can get absorbed into your skin.
That can potentially cause health issues in some people.
I have written on my skin with permanent marker for years and nothing bad has happened but there's still the possibility of getting poisoned from the chemicals that are in the permanent marker.
Regular colored markers that kids use such as Crayola markers do not contain any toxic chemical so writing on your skin with those markers is not bad.
Permanent marker will stay on skin for around 3 days before it starts to fade away.
When writing on your skin with permanent marker the permanent marker will eventually come off of the skin overtime.
Even if you do not remove the permanent marker from your skin the permanent marker will fade and completely disappear from the skin.
However you can use some rubbing alcohol or acetone based nail polish remover to get the permanent marker off the skin.
It's not recommended to write on your skin with permanent marker but it's not really gonna harm you if you do.
I've written on my skin with permanent marker for years and never gotten sick from it.
But it's not recommended to do so.