Inositol

INCI: Inositol 

Category: Sugar Alcohol / Humectant / Sebum-Regulating Active 

Used in: Moisturisers, serums, scalp treatments, oil-control formulas, supplements (oral) 

Typical Usage Level (Topical): 0.5–3% | 

Oral: 2–4g/day (therapeutic range; consult healthcare provider)

What This Ingredient Does

Inositol is a naturally occurring sugar alcohol found in plant foods and synthesised endogenously by the body. Structurally, it is a key component of phospholipid cell membranes (as phosphatidylinositol), where it plays a role in signal transduction the process by which cells receive and respond to external signals. In skin, this structural role supports cell membrane integrity and contributes to hydration retention at the cellular level. Topically, inositol functions as a mild humectant and has shown evidence of modulating sebocyte activity, reducing excess sebum output in oily and acne-prone skin. Orally, inositol is well-studied in the context of hormonal regulation particularly in PCOS, where insulin resistance drives androgen excess and subsequent sebum overproduction and hair thinning. Supplementation has been shown to improve insulin sensitivity, reduce androgen levels, and support more regular menstrual cycles, with downstream benefits for acne and hormonal hair loss.

In scalp and hair supplement formulas, works alongside Biotin and Iron (Chelated) to address nutritional contributors to hair thinning.

Key Benefits

• Supports cell membrane integrity as a structural phospholipid component

• Mild humectant function improves skin surface hydration

• Reduces sebum output in oily and acne-prone skin via sebocyte modulation

• Oral supplementation improves insulin sensitivity and reduces androgen-driven acne and hair loss in PCOS

• Supports hormonal balance relevant to both skin clarity and hair retention

Who It's Best For

• Oily or acne-prone skin requiring gentle sebum regulation without drying actives

• Women with PCOS-related acne, excess facial hair, or hormonal hair thinning (oral supplementation under medical guidance)

• Those looking to support skin hydration through membrane-level cellular health

• Can be used topically and orally for complementary benefit in hormonally driven skin and hair concerns

Clinical Note by Dr. Su

Inositol is one of the more interesting ingredients that crosses the skin-gut-hormone axis. Topically, its sebum  modulating effect is modest but real. Orally, the evidence in PCOS is more substantial myo-inositol supplementation has shown consistent results in reducing androgen levels and improving skin and hair outcomes in this population. If a patient presents with PCOS related acne or hair thinning, inositol is one of the first supplements I consider alongside a blood panel.

References

• Unfer V, et al. (2016). Myo-inositol effects in women with PCOS: a meta-analysis. Endocrine Connections. PMC5002115

• Formoso G, et al. (2015). Short and long term effects of myo-inositol supplementation in women with metabolic syndrome. European Journal of Nutrition. PMID: 25552320