Does oily skin really overproduce sebum when dehydrated?

NOTE: Click here to read the follow up post on sebum regulation.

Al4galm asks…I have read many blogs, articles, etc that claim that oily skin produces more oil when is dehydrated. Is it true?
None of them reference studies.

The Beauty Brains respond: 

None of them referenced studies???  I’m tempted to report the bastards to the United Federation of Beauty Bloggers! Seriously though, if you do find a beauty blog that documents its sources of information you should bookmark it and sleep with it under your pillow! But back to your question…

The science of sebum

The answer lies in how sebum production is regulated – in other words what turns the sebum glands on and off. It’s not the presence or absence of moisture that triggers the production of oil, it’s the presence of sebum on the surface of skin. According to a study published in the Archiv für dermatologische Forschung, researchers stripped oil off skin and then measured how long it took the skin to re-oil itself. Their data indicates that the presence of oil on the skin’s surface sends a signal to the sebaceous glands to turn off. This signal is caused by either the pressure of the oil in the follicle or by the creation of a chemical signal that travels back down through the skin.

So it looks like it’s the amount of oil on the skin and not the degree of dehydration that determines how much oil the glands produce.