Hair really is dead in the most technical and accurate sense. There is no life on a cellular level at all. The absorption/loss of moisture isn't regulated as much as it is consequential to strand porosity balanced with environmental humidity (or lack thereof). Lower porosity hair resists moisture changes because the cuticle lies very flat, with little room for moisture to enter or exit. Higher porosity hair has a more roughened or opened cuticle, so moisture moves in and out more quickly.
As far as damage due to moisture, it is theoretically possible, but probably very highly unlikely (it's much more common for damage to be caused during the drying process - IAGirl had an amazing blog explaining how heat- in the sense of the very rapid drying of hair- can cause damage to the cuticle).
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3a/f/iii Before the chop- Donated to Locks of Love, January 2013
Modified CG since 11/5/11
CO-WASH: VO5 Vanilla Mint Tea Clarifying, DevaCare No-Poo
CLARIFY: CHS Treatment Shampoo (used prior to PT/DT)
RO: DevaCare One Condition, Regis Olive Oil
LI: Cure Care, As I Am Leave-In
STYLE: Re:Coil, Curl Keeper, Biotera Gel, Deva Ultra Defining Gel, GVP Liquid Sculpting Gel, Curls Rock Amplifier and Strong Hold Mousse
PT/DT: IAGirl's PT, One n' Only Argan Hydrating Mask