Reference
Problematic Ingredients and Their Mechanisms of Harm
| Ingredient | Role in Formula | How It Damages the Scalp |
|---|---|---|
| Sodium Laureth Sulfate (SLES) | Primary anionic surfactant; creates foam, removes oil/dirt | While milder than SLS, SLES still disrupts the stratum corneum lipid matrix, increases transepidermal water loss (TEWL), strips natural moisturizing factors (NMFs), and raises scalp pH above its ideal 4.5–5.5 range. Chronic use compromises barrier integrity, allowing irritant penetration and triggering irritant contact dermatitis (ICD). Research shows SLS/SLES-containing wash products exacerbate barrier dysfunction — increased TEWL, decreased hydration, and elevated skin redness are measurable within days of repeated exposure. |
| Dimethicone | Non-water-soluble silicone; emollient, hair-conditioning film-former | Dimethicone coats each hair shaft and deposits on the scalp surface. Because it is not water-soluble, it accumulates with repeated use. This occlusive film traps sebum, sweat, dead skin cells, and bacteria against the scalp, potentially clogging hair follicles (follicular occlusion). Over time, this creates an environment that promotes inflammation, itchiness, and in severe cases folliculitis. The buildup also prevents moisture from penetrating the hair shaft, paradoxically drying hair out over time despite the initial smooth feel. |
| Polyquaternium-64 | Cationic conditioning polymer; mimics skin phospholipids, binds to negatively charged hair | Though water-soluble and generally less buildup-prone than some polyquats, Polyquaternium-64 still leaves a cationic film on both hair and scalp. When combined with dimethicone in the same formula, the two film-formers compound each other — the silicone creates a water-repellent layer that the polyquat film sits on top of. For sensitive scalps, quaternary ammonium compounds can trigger allergic contact dermatitis in predisposed individuals. Repeated deposition without adequate removal (especially when using a gentle or co-wash routine) leads to layered accumulation. |
| Fragrance (Parfum) | Sensory/aesthetic | Fragrance is among the top allergens in scalp contact dermatitis. The NACDG data identifies fragrance mix I and Balsam of Peru as significant scalp allergens. For a barrier already compromised by SLES, fragrance compounds penetrate more easily, amplifying irritation. |
| Glycol Distearate | Pearlizing agent (creates the opalescent appearance) | A waxy ester that can contribute to buildup on the scalp surface, adding another occlusive layer alongside dimethicone. |