1). Almost, all organic solvents pass across the skin. But exceptionally, the highly toxic methanol further passes into the systematic circulation because it is a very small molecule. Therefore and apart drinking and inhalation, systematic intoxication from methanol also occurs by skin and eye absorption.
As Babcock_Hall has descibed above, the toxicity of methanol is due to the liver microsomal oxidation, in vivo, to formaldehyde that causes tissue necrosis (mummy syndrome). Contrary, ethanol is oxidized to acetaldehyde that simply causes a “hungover” the next day.
Skin absorption is an equilibrium effect, meaning that a fraction of absorbed methanol is simultaneously skin excreted. As a consequence, systematic intoxication from methanol by the skin, demands high methanol amounts and long contact times.
2). Methylated spirits and other organic solvents dehydrate the skin and thus, rash, eczema and dermatitis might appear after prolonged (repeated) use. Therefore, solvent-resistant vinyl gloves must be used, while intensively working with these solvents.
3). But it’s not that all solvents are dangerous for the skin. Indicatively: ethanol, IPA, glycerol, polyethylene glycol, mineral oil (Nujol), paraffin oil (Vaseline) and many others are widely used in skin care and cosmetic formulations.