Inositol

Inositol (myo-inositol) is a skin-conditioning/humectant ingredient typically used at low percentages and is highly water-soluble, with a long history of good tolerability in leave-on formulations. Clinical experience and patch-test data suggest a very low rate of irritant reactions, though any leave-on ingredient can rarely sting on severely compromised eczema skin. Given its minimal inherent reactivity and low sensitization potential, it fits the 'exceptionally gentle' category rather than fully inert. Safety Notes: Inositol is used in many commercial skin and scalp products primarily as a humectant/skin-conditioning and barrier-support ingredient, where it often appears at low “label” levels (~0.01–0.3%) in multi-ingredient leave-on serums/creams and in rinse-off cleansers. In more targeted OTC offerings (e.g., hydrating/barrier formulas, scalp tonics, and some anti-breakage hair/skin treatments), inositol is formulated at ~1–5% as a primary polyol-type active; above ~5% is uncommon in consumer skincare due to solubility/processing limits and increasing tackiness, and there is no specific EU/FDA concentration cap for inositol in cosmetics.