While companies love to boast about how much water their products can put in your skin, it turns out that may not be a good thing because too much water is particularly hard on dry skin. Overhydration can indeed be a problem, and products that brag about increasing water content in skin cells by 180% can be doing more harm than good.
This contention isn’t new, and was supported in an article in Cosmetics & Toiletries magazine (May 2000, page 18). The article reviewed a book by Loden and Maibach called Dry Skin and Moisturizers, Chemistry and Function. One of the points in this book that impressed the reviewer was the fact that “prolonged water contact is not innocuous.
Intense dermatitis can occur simply by prolonged water exposure…. Water alone also disrupts the SC [stratum corneum—the outer, surface layer of skin]….” Their studies show that water can directly disrupt the barrier lipids [the substances that protect the surface of skin and are similar to how skin is disrupted when washed with strong cleansers].
That means water can break down the stuff that binds skin cells together, actually degrading skin in the same way that strong cleansing agents can. (Note: Cosmetics & Toiletries magazine is a cosmetics industry journal read by cosmetics executives, formulators, and packaging companies.) Another article, in Contact Dermatitis (December 1999, pages 311–314), stated that “Water is a skin irritant, which deserves attention because of its [pervasiveness].
In occupational dermatology, the importance of water as a skin irritant is especially appreciated. The irritancy of water has been demonstrated by occlusion experiments; occlusion with either closed chambers or water-soaked patches has been shown to produce clinical and histopathological inflammation.
Functional damage, as revealed by increased transepidermal water loss, has also been shown…. However, much remains to be done to clarify the risk factors and mechanisms of water-induced irritation.