No one knows exactly why skin feels tight after cleansing, however one general theory is widely accepted. Soap is a simple anionic surfactant with a high pH. The high pH causes swelling of the stratum corneum, which allows unwanted deeper penetration of the soap into the skin possibly causing irritation and itching. The soap also binds to stratum corneum proteins further inducing swelling and hyper-hydration of the skin. Following the completion of washing, the excess water evaporates leading to skin tightness and dryness because the soap binding reduces the ability of the skin proteins to hold water. This explains the reduction in skin hydration and elasticity following soap cleansing.
More Cosmetic Conundrums: