The humectant use in high/low humidity climate is happening too for the skin but it’s much much less intense than with hair. Our skin is a living organ with a protective barrier and loots of layers designed to protect our skin moisture from the environment so applying some humectants is in general not so much of an issue in terms of moisture loss or bloating. However if you’re in hot humid climate, a scalp toner may create a breeding ground for bacteria and/or yeast if it’s not well adjusted to the skin type or fully absorbed so it’s important to stay mindful how you use it and make sure you keep up with regular cleanses.