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. 2021 Apr;7(3):183-193.
doi: 10.1159/000512786. Epub 2021 Feb 15.

The Impact of Shampoo Wash Frequency on Scalp and Hair Conditions

Supriya Punyani  1 , Antonella Tosti  2 , Maria Hordinsky  3 , Dawn Yeomans  4 , James Schwartz  4
Affiliations

The Impact of Shampoo Wash Frequency on Scalp and Hair Conditions

Supriya Punyani et al. Skin Appendage Disord. 2021 Apr.

Abstract

Background: How frequently should the scalp and hair be cleansed? A dearth of objective data has led to confusion both among lay people and experts. Each extreme has potential detrimental effects: overcleaning may lead to surface damage while undercleaning may lead to buildup of harmful stimuli. This situation is complicated because both objective and subjective criteria are relevant to assess optimal cleaning.

Objectives: The objective of this work was to combine epidemiological and treatment data with both objective and subjective end points to yield clear data to guide both the consumer and expert as to optimal scalp and hair cleaning practices.

Methods: Two studies were conducted with Asian populations without any specific scalp pathologies. An epidemiological study was conducted as a function of natural wash frequency. This was combined with a controlled wash frequency study. In both cases, objective measures of hair and scalp condition were assessed. These were combined with self-assessments of all participants.

Results: In the epidemiological study, it was observed that overall satisfaction with hair and scalp condition was achieved when washing 5-6 times per week. This was consistent for both objective and subjective end points. Controlled treatment likewise showed that a daily wash regimen was superior to once per week cleansing for all end points. No objective detrimental effects to hair at this level of cleansing were observed.

Conclusions: Two different studies led to the same conclusion: higher wash frequency is both beneficial and more preferred to lower wash frequency among the Asian populations studied. Concerns related to "overcleaning" were unfounded both objectively and subjectively.

Keywords: Epidemiological; Hair; Oxidative stress; Scalp; Shampoo frequency; Treatment.

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Conflict of interest statement

S.P. and J.S. are employees of the Procter & Gamble Company, which paid 100% of the costs of this work.

Figures

Fig. 1
Fig. 1
Example of hair type and texture of recruited females in the epidemiological study.
Fig. 2
Fig. 2
Scalp Flaking Score graded by experts as function of wash frequency in epidemiological study. The mean ASFS is plotted with standard error bars. Results not connected by same letter are significantly different. ASFS, Adherent Scalp Flaking Score.
Fig. 3
Fig. 3
Self-perceived scalp parameters dandruff, itch, and dryness of n = 1,500 males and females as function of wash frequency in the epidemiological study. The mean is plotted with standard error bars. Results not connected by same letter are significantly different.
Fig. 4
Fig. 4
Self-perceived hair attributes hair loss, hair brittleness, and hair not smooth of n = 1,500 males and females as function of wash frequency in the epidemiological study. The mean is plotted with standard error bars. Results not connected by the same letter are significantly different.
Fig. 5
Fig. 5
Self-perceived of number of “great hair days” improved for n = 1,500 males and females as function of wash frequency. The mean is plotted with standard error bars. Results not connected by the same letter are significantly different.
Fig. 6
Fig. 6
Technical scalp measurements for total sebum lipids (normalized CH-stretch PA) (a), oxidized lipids (HODE-9) (b), flaking score (ASFS) (c), and odor intensity at 7-day refrain (yellow bar) and daily wash (blue bar) (d). For each measurement, lower value indicates healthier scalp. ASFS, Adherent Scalp Flaking Score.
Fig. 7
Fig. 7
Selected scalp images comparing the oil accumulation representative of the 7-day refrain and daily wash protocols.
Fig. 8
Fig. 8
Technical hair measurements for total sebum lipids (a), oxidized lipids (HODE) (b), greasy shine (c), and % water uptake at 7-days refrain (yellow bar) and daily wash (blue bar) (d). For measurements in (a, b, d), lower value indicates healthier hair. For measurement in (c), lower value indicates a less greasy shine on hair.
Fig. 9
Fig. 9
Selected hair images comparing the oil accumulation representative of the 7-day refrain and daily wash protocols.
Fig. 10
Fig. 10
Quantification of internal hair lipids using GC method as a result of 7-day refrain and daily wash protocols. No significant differences were observed.
Fig. 11
Fig. 11
Improvement of self-perception of hair (a) and scalp (b) attributes upon switching from 7-day refrain versus daily wash protocol. A categorical scale 0–10 was used for the worst of the conditions panelists had during the last 24 h, where 0 = none and 10 = worst imaginable. p values are based on pairwise t test.
See this image and copyright information in PMC

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