Glycerin: Moisturising or Drying ?

Glycerin is supposed to be a wonderful moisturiser, as it has the property of drawing moisture from the environment onto your skin. Or out of your skin.

Edit: this post has been re-written as I have learned much more about the topic since I wrote this.

  Depending on the humidity of the air, Glycerine may draw moisture from the deeper layers of the skin and hold it on the skin surface. It may also attract too much moisture from the air, causing frizz.
 Like most humectants, glycerin works best in medium humidity (dew point between 1.5 - 10°C).If you´re buying or DIYing a cosmetic with glycerin among it´s ingredients, make sure there is also an emollient in it. The emollient prevents the skin or hair from taking in too much moisture or drying out. Recommended emollients are plant oils, water-soluble silicons and lanolin. Humidity, dew point and humectants are explained *here*

Besides, Glycerine (Glicerol) is listed on MSDS as hazardous:
"May cause eye and skin irritation. May cause respiratory and digestive tract irritation. Repeated contact may cause dehydration of skin.Personal protection: Minimise contact."
Found in: moisturisers, shampoos, shaving creams, moisturisers...

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