Dry hair is one of the most frequently reported problems in the salon — and one of the most misunderstood. Saying that hair is “dry” is not enough: depending on whether the dryness is of cuticle, cortical, or sebaceous origin, the effective actives are fundamentally different. Hairswiss analyzes the mechanisms of hair dehydration to help professionals formulate a precise technical response.

What Is Hair Dryness? Three Distinct Mechanisms

The hair fiber maintains its optimal hydration level (between 10 and 15% of its weight in water) thanks to two complementary systems. The first is the NMF (Natural Moisturizing Factor), a complex of endogenous humectants located in the cuticle cells — mainly pyrrolidone-carboxylic acid (PCA), free amino acids, urocanic acid, and lactate. The second is the CEW (Cell Envelope Wax), an intercellular lipid layer composed of 18-methyleicosanoic acid (18-MEA) that forms a hydrophobic barrier preventing transfibrillary water loss.

Depending on the mechanism involved, three types of dryness can be identified:

• Lipid dryness: the CEW is depleted by sulfated detergents, repeated alkaline treatments, or UV exposure. The cuticle loses its impermeability: water evaporates freely, and the hair absorbs and loses moisture chaotically depending on ambient humidity. This is hygroscopic frizz.
• Protein dryness: the cortex is depleted of keratin (through bleaching, perming, or straightening). The fiber becomes hyper-porous: it absorbs water excessively but cannot retain it. Paradoxically, this type of hair appears moist but breaks easily when it dries.
• Sebaceous dryness: the scalp produces insufficient sebum, the natural protection that lubricates and protects the fiber from the root. A problem of physiological origin (genetic, hormonal, environmental), treated at the scalp level, not the fiber level.

Humectants, Occlusives, Emollients: Understanding the Categories of Moisturizers

Humectants: Attracting Water

Humectants are hygroscopic molecules that capture water molecules from the air or from the deep layers of the fiber and maintain them in the target zone. The most used in hair care:

• Hyaluronic acid (sodium hyaluronate): polysaccharide with high water retention capacity — up to 1000 times its weight. Low molecular weight forms (<50 kDa) penetrate the fiber; high molecular weight forms create a surface film.
• Panthenol (prov. vitamin B5): hydrolyzes to pantothenic acid once in the fiber. Humectant and mildly film-forming, it improves the elasticity and suppleness of keratin.
• Glycerin: effective triol, but which can become counterproductive at high humidity, where it attracts too much water and causes excessive fiber swelling.
• Sorbitol, sodium PCA, betaine: secondary humectants frequently combined to optimize the hydration profile.

Occlusives: Blocking Water Loss

Occlusives form a physical barrier on the fiber surface that slows transfibrillary water loss. The most used:

• Oils rich in oleic acid (C18:1): argan, camellia, jojoba. Their small molecular size allows them to partially penetrate the cortex and restore intercellular cement.
• Plant butters (shea, mango): heavy occlusives to be used in low concentrations on lengths — risk of weighing down at high doses.
• Silicones (dimethicone, cyclomethicone): very effective synthetic occlusives, but not biodegradable. They do not penetrate the fiber — their effect is purely surface-level and can accumulate (build-up).

Emollients: Softening and Smoothing

Emollients improve glide between cuticle scales and reduce the friction coefficient. This category includes fatty acid esters (cetyl esters, isopropyl palmitate) and certain light silicones (cyclopentasiloxane). They do not directly moisturize but considerably improve tactile feel and combing ease.

Professional Protocol: Diagnose Before Formulating

A rigorous professional begins by identifying the type of dryness before choosing the treatment. Some simple diagnostic tests:

• Porosity test: a hair placed in water sinks quickly if the cortex is exposed (high porosity). It floats if the cuticle is intact.
• Elasticity test: a healthy wet hair can stretch 20-30% before breaking. Immediate breakage indicates a cortex depleted of keratin.
• Tactile observation: hair that feels rough when sliding toward the tip signals lifted cuticle scales — surface lipid dryness.

Depending on the diagnosis, the appropriate treatment will vary: high-porosity hair needs hydrolyzed proteins (cortical reconstruction) even before humectants. Hair with a damaged cuticle but intact cortex requires reconstructive lipids first (18-MEA, penetrating oils), then humectants to stabilize hydration. What Swiss hair professionals can find on cliCHair.ch: ranges structured by hair diagnosis, with targeted actives according to the fiber’s degradation level. Among the representative products, the Reconstructive Mask by Edelstein, which combines hydrolyzed keratin, hyaluronic acid, and macadamia oil for molecular reconstruction suited to protein and lipid dryness.

Key Takeaways

Hair dryness is not a uniform condition. It is a differential diagnosis that requires distinguishing the lipid, protein, or sebaceous origin of the problem before prescribing a treatment. Not all “moisturizing” actives are equivalent — and a humectant applied to a hyper-porous cortex without reconstructed proteins can worsen fiber swelling rather than improve it.

Hairswiss will cover each family of moisturizing actives in detail in upcoming articles: hyaluronic acid, panthenol, 18-MEA, and bond builders — their chemistry, their positioning in the fiber, and their compatibility with technical services.