Intrinsic and Extrinsic Skin Aging: What Can We Control?

As a cosmetic chemist you may be requested to create a skin anti-aging product.  But did you ever wonder what you can actually control?  There are two ways in which skin aging occurs, intrinsic or chronological aging and extrinsic aging related to factors like sun exposure and smoking.

Intrinsic aging

Intrinsic aging is a gradual degradation that takes place over time on all body sites. In aged skin the synthesis of collagen, which provides structure to the dermis, is diminished and increased levels of matrix metalloproteinase contribute to degradation of existing collagen. Elastin fibers become disorganized and less effective. Other changes include increased dryness, flattened papillary dermis, and decreased stratum corneum turnover. Gravity and facial expressions, although some might consider extrinsic, can’t be fully avoided and I tend to think of them as part of the intrinsic aging process.

Extrinsic aging

Extrinsic aging is brought on by external factors and accelerates intrinsic aging. We can exert some level of control over extrinsic factors. Sun exposure and smoking are two factors we currently know the most about. In fact, a recent study comparing identical twins further confirmed the role of these two factors in accelerated skin aging(1).  These effects take time to surface. So if you or someone you know needs an additional reason to quit smoking or break the tanning habit, take a look at the paired images from this study and perhaps vanity will persuade.


While some exposure to the sun is healthy, due to synthesis of Vitamin D and its mood boosting ability, tanning and erythema (redness) are indications of damage. Although UVB is the culprit in sunburns, it is the UVA portion of the spectrum that causes deeper damage. Production of collagen degrading MMPs are stimulated, abnormal elastin deposits accumulate in a condition known as solar elastosis, and vascular factors which encourage telangiectasia, or spider veins, are produced. Additionally, irregularities in melanin production result in uneven skin tone and age spots. Repeated long-term exposures can cause more serious skin damage manifesting in conditions like actinic keratoses or skin cancers.


Nicotine in cigarettes constricts blood vessels limiting availability of oxygen and nutrients to the skin. The number and depth of wrinkles are increased while repeated facial movements also cause a higher degree of wrinkling around the mouth and eyes.

1. Guyuron B, Rowe D J, Weinfeld AB ,Eshraghi Y, Fathi A, Iamphongsai S. Factors Contributing to the Facial Aging of Identical Twins. Plastic & Reconstructive Surgery; 2009. Vol. 123, pp1321-1331.

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