Clay is pretty amazing, isn't it? You can make art with it, you can slap it on your skin, you can even eat it for digestive problems! I'm only going to talk about how great it is for your skin today, but I thought we should take a moment to appreciate how useful mud is, except when it gets on your car/shoes/dog. Ok, done.
One of the things that always makes my oily skin feel clean and refreshed is a clay mask. Clay is very absorbent, and no doubt part of the "clean" feeling is just the clay temporarily tightening my skin by drying it out... but clay also sucks oil out of your pores, and any other crap that's currently dissolved in the oil, that could later oxidise and form plugs and blackheads. This is why pores seem to shrink right after a clay mask!
There's not much published scientific research on clay - however, one recent study found that daily clay applications on rats increased the number of collagen fibres. Clay has also been found to speed up collagen synthesis in skin lesions - since loss of collagen is one of the causes of old-looking skin, this might be why clay is so popular!
However, there are lots of different types of clay, containing different proportions of minerals. There are a lot of conventionally accepted recommendations for which clay to use for your skin:
Kaolin - this is an all-purpose clay that's good for all skin types, including sensitive skin. It's said to soothe irritated skin and soak up oil.
Green French clay - this clay sucks all your oil out! Good for oily skin.
Bentonite - this is the main component of "volcanic ash" clays. It's good for normal and oily skin.
These are the most common clays used in skincare, but there are plenty more!
Check back in a few days for my DIY in-shower clay scrub/lazy mask recipe :)
C Viserasa, C Aguzzib, P Cerezoa and A Lopez-Galindoc. Uses of clay minerals in semisolid health care and therapeutic products, Appl Clay Sci 2007, 36, 37.
DMZ Valenti, J Silva, WR Teodoro, AP Velosa and SBV Mello. Effect of topical clay application on the synthesis of collagen in skin: an experimental study. Clin Exp Dermatol 2012, 37, 164.