Hair salon in Olbia · Total Look
The science of shampoo
Shampoo cleans through surfactants — molecules that trap sebum and dirt so water can rinse them away. The ideal pH stays at or below 5.5, sulfates are safe but can over-strip, and the right wash frequency depends on your scalp, not on a universal rule. Here is what the research actually says.
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How shampoo cleans
Surfactants are molecules with a water-loving head and an oil-loving tail: they surround sebum and residue and keep them suspended in water until you rinse. How strongly a shampoo cleans depends on the type and amount of surfactants in the formula (D'Souza & Rathi, Indian Journal of Dermatology).
Sulfates: what the evidence shows
A 2015 peer-reviewed safety review found no evidence that sodium lauryl sulfate causes hair loss, and no evidence it is carcinogenic — irritation is dose- and contact-time-dependent. "Sulfate-free" means gentler, not safer: it cleans less aggressively, which suits dry, curly or colour-treated hair.
pH really matters
The scalp is naturally acidic (about pH 5.5). A study of 123 commercial shampoos (International Journal of Trichology, 2014) found 61.8% exceeded pH 5.5 — and alkaline pH increases fibre friction, worsening frizz and breakage. Notably, 75% of the professional salon shampoos tested were at the correct pH (≤ 5.5).
How often should you wash?
The American Academy of Dermatology gives no universal frequency: it depends on how quickly your scalp gets oily. Straight, oily hair may need daily washing; curly, thick or treated hair can wait longer. Frequent washing does not damage hair: in a 2021 clinical study, daily washing beat weekly washing on every measured scalp and hair parameter, with satisfaction peaking at 5–6 washes per week.
Dry shampoo: useful, but it doesn't clean
Dry shampoo absorbs oil with starches and powders, but removes no dead skin cells or build-up: AAD dermatologists say it is not a substitute for washing, and recommend at most one or two uses between water washes to avoid residue, breakage and seborrheic dermatitis.
The myth to retire
"Washing makes your hair fall out" — false. The hairs you see in the drain were already in the telogen (resting) phase and would have shed anyway; washing dislodges them, it doesn't cause the loss. The AAD clearly distinguishes physiological shedding (50–100 hairs a day) from pathological hair loss.
Sources
- American Academy of Dermatology — Tips for healthy hair
- AAD — Dry shampoo: dermatologists' tips
- AAD — Hair loss or hair shedding?
- Gavazzoni Dias et al., "The Shampoo pH can Affect the Hair: Myth or Reality?", Int. J. Trichology 2014
- Punyani et al., "The Impact of Shampoo Wash Frequency on Scalp and Hair Conditions", Skin Appendage Disorders 2021
- Bondi et al., "Human and Environmental Toxicity of Sodium Lauryl Sulfate", Environ Health Insights 2015
- D'Souza & Rathi, "Shampoo and Conditioners: What a Dermatologist Should Know", Indian J Dermatol
Last updated: June 2026