I love some of the other things in the Pureness line (blotting papers are an HG product for me), so I thought I was going to like this moisturizer for my oily t-zone and décolletage, which are both very breakout prone. I have never actually seen any instructions that say it can be used on the décolletage, but I haven't seen any that say not to. As for the t-zone, this definitely did mattify, but it only lasted around an hour, and I think it made me oilier, like the oil was waiting to burst through, and it made my makeup ball up. It also gave me 2 milia on my forehead and a lot of blackheads on my face. But the thing that made me most upset about it was that it made my décolletage break out horribly, in blackheads, whiteheads and several pustules. It was so bad that I had to avoid wearing anything that showed that area at all for a few weeks, even if I covered it with body foundation and heavy concealer. From now on, I will stick to oil free moisturizers for these areas, but won't use anything mattifying.