There are two types of skin aging that occur at the same time: intrinsic and extrinsic. Intrinsic skin aging is caused primarily by internal factors within the body, such as genetics and the normal aging processes. Extrinsic skin aging, or photo-aging, is caused by environmental factors such as sunlight and lifestyle habits such as smoking. With each passing year, the average moisture content of the stratum corneum decreases gradually as a result of hormonal changes that, over time, cause a reduction in sebum production. Cigarette smoking profoundly affects skin aging, as nicotine intake expedites the breakdown of skin cells.Want to read more? Subscribe to one of our monthly plans to continue reading this article.