I have been using a nasal pillow with no real problems, but wanted to try a full face mask as an alternative. I got a Quattro FX, which was surprisingly comfortable, but after the second night I had to stop using it because of a nasty skin reaction where the silicone seal rested on my face: a red ring of inflammation around my nose and mouth that lasted most of the day. It wasn't from too much pressure, but seemed chemical in nature, similar to what I get from certain bandage adhesives.
After a bit of searching on CPAP discussion boards, I found a post saying that mask seals should always be washed before using them the first time; a reply suggested soaking new silicone seals in a hot solution of baking soda. So I followed their recipe and boiled 4 cups water, added 2-3 teaspoons baking soda, gave it a stir, dropped in the seal, knocked out any air bubbles, let it soak until the solution came to room temperature, then rinsed it well. I didn't use soap. The original crystal clear transparent silicon rubber became milky translucent after the treatment, but it was just as pliable and gave no more irritation! For the daily washing of my mask seal I don't use soap, but just warm water and rub it with my fingers until it squeeks.
Given all that, however, I ended up using a mask liner (RemZzzz) because I don't like the sweaty feeling that develops during the night under the full face seal.