We've all heard about the three skin types -- dry, oily, and normal. If you want to count combination skin, that makes it four skin types. There are many books, magazine and internet articles with various strategies for taking care of your skin based on your skin type.
It seems like there's a science to taking care of your T-zone, but is it really science? Have you ever asked your doctor about skin care for your type and noticed that you didn't get a straightforward answer?
The reason your doctor doesn't (or shouldn't after reading this) base your skin-care regimen on your skin type is because there really is no science behind the three skin types. There are no published studies on the physical characteristics that separate skin into dry, oily, or normal types.
The truth is the skin doesn't really have a "type." There are factors that are components of healthy skin, but using a broad term like "oily" or "dry" does not accurately determine your skin care. Furthermore, skin diseases affect all "skin types" and have to be considered in a skin-care regimen.
It's better, and easier, to know what makes skin healthy and focus your skin care on taking care of problem areas while maintaining the healthy factors.
Sources:
Ambroisine, Laurence, et al. "Relationships between visual and tactile features and biophysical parameters in human facial skin." Skin Research and Technology 13(2007): 176-83.
Nouveau-Richard, S, et al. "Oily skin: specific features in Chinese women." Skin Research and Technology 13(2007): 43-8.
Youn, Sang, et al. "Evaluation of facial skin type by sebum secretion: Discrepancies between subjective descriptions and sebum secretion." Skin Research and Technology 8(2002): 168-72.
