Due to several recent posts from other readers on this same subject, this is a repetition of a post that I did a few years ago (complete with medical references):

Journal of Investigative Dermatology. 1987 Mar;88(3 Suppl):2s-6s.

"Skin lipids: an update"

Downing DT, Stewart ME, Wertz PW, Colton SW, Abraham W, Strauss JS.

(excerpt from this study follows below, including the references...)

Sebum and Dry Skin "...skin can be healthy and have charming cosmetic properties in the virtual absence of sebum." (14)

Kligman drew attention to prepubertal children, who produce almost no sebum, to support his thesis that skin does not depend upon sebum for maintaining its barrier to water loss: "...there can be no doubt of the insignificance of sebum as a waterproofing material." (14) Our recent studies at the other end of the human age spectrum have supported this conviction. In a survey of sebum secretion rates and the incidence of dry skin among subjects aged 65 to 97, no correlation was found between sebaceous gland activity and the presence or severity of dry skin (34). Kligman recognized that sebum could mask the scaliness of dry skin without producing any actual change in the condition: "Sebum, like any oil, has some emollient or smoothing effect when a sufficient quantity is rubbed into dry, scaling skin." (14) In spite of the clear inference to be drawn from the cutaneous characteristics of children and the experimental data obtained from the elderly, it remains difficult to dispel the myth that low sebum secretion rates cause dry skin. It is a rare individual who realizes that "dry" is not the obverse of "oily".

(14) Kligman AM: The uses of sebum. Br J Dermatol 75: 307-319, 1963

(34) Frantz RA, Kinney CK, Downing DT: A study of skin dryness in the elderly. Nursing Res 35: 98-100, 1986.