What does propylene glycol do to hair?

I'm curious to know, what specific effects does propylene glycol have on hair? Is it a commonly used ingredient in hair care products? And if so, what are the benefits or potential drawbacks of its inclusion? Does it play a role in enhancing the texture, shine, or health of hair, or could it potentially cause any irritation or damage? I'd appreciate a detailed explanation of propylene glycol's role in hair care and any precautions that should be taken when using products that contain it.