Are you
Sweat
I appear when you're exhausted,
But not when you're frosted.
You you are hot you sweat.
In heat, I'll appear.
If I don't, you should fear.
When you got hot your body wets itself to cool down.
They think I'm disgusting,
But I just show you, you're adjusting.
Sweaty socks are shown as dirty, and you sweat to get used to heat.
I'm a natural part of life,
In dance or sickness, I am rife.
>!It is normal to sweat when you are active, when you have a fever, or just staying still.
Regarding the title
Sweat is liquid and it reflects sun light, therefore it glistens.