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
Modified CG since 11/5/11
CLEANSE: CJ Daily Fix, DevaCare No-Poo, CHS Treatment Shampoo
RO: SS Caitlin's Conditioner, CJ Beauticurls Strengthening
LI: SS Repairing Protein Treatment, CHS Silk Leave-In
STYLE: Re:Coil, Curl Keeper, Deva Ultra Defining Gel, Curls Rock Amplifier,Sweet Curls Elixirs Okra Gel and Hard Hold Gel, SS Curl Enhancing Jelly and Firm Hold Gel