The Impact of Shampoo Wash Frequency on Scalp and Hair Conditions

Weekly hair washing: The recommended solution for women with afro-textured hair to alleviate dandruff and scalp discomfort

Dandruff and scalp discomfort are common concerns for women and men in Africa. Moreover, women with afro-textured hair are prone to scalp discomfort owing to irregular hair washing, frequent use of oil-based products on their scalp, and harsh chemical treatments. Current literature does not, however, provide data on the pathophysiological mechanisms of these conditions in this population. In this study, we investigated the mechanisms behind scalp discomfort and dandruff in women of African descent before and after hair washing. We conducted the in Durban, South Africa, over a 3-week period with 60 women of African descent aged 20-40 years. The respondents were equally divided into a "dandruff" and a "no dandruff" group, based on clinical grading of adherent dandruff by a dermatologist. Malassezia spp. and bacterial loads were quantified by quantitative polymerase chain reaction. Evaluations of scalp condition and sample collection were performed at five time points during the 3 weeks. Data on discomfort symptoms were collected via a self-assessment questionnaire. We observed that the dandruff severity peaked at the end of the first week after hair washing and plateaued from thereon in both groups. Dandruff was associated with higher Malassezia and bacterial load counts and there was a direct correlation between the Malassezia spp. load and dandruff score. Via self-assessment questionnaire responses submitted by participants, we observed that itching was the most pronounced scalp discomfort, compared with the sensation of tingling and burning at baseline, while an improvement of the scalp symptoms of dandruff and itch was observed in both groups after one hair wash. The study also showed that higher colonization with Malassezia spp. and bacteria is associated with dandruff independently of the time point, confirming a scalp microbiome contribution to the dandruff pathophysiology in the study population. The benefits of washing were, however, not sustained after 1 week and we thus recommend weekly hair washing for long-term management of dandruff and scalp itchiness in this population.

Seborrheic dermatitis: topical therapeutics and formulation design

Seborrheic dermatitis (SD) is a common dermatological disorder with symptoms that include skin flaking, erythema and pruritus. This review discusses the topical products available for treating SD, which target several aspects of disease pathobiology, including cutaneous microbial dysbiosis (driven by Malassezia yeast), inflammation, sebum production and skin barrier disruption. Among the various treatments available, zinc pyrithione (ZnPT) based products that exhibit anti-fungal action are the market leaders. A skin compartment approach is presented here for combining ZnPT exposure information with threshold levels for anti-fungal efficacy and toxicity, overall providing a comprehensive picture of ZnPT therapeutics and safety. While Malassezia yeast on the surface are effectively targeted, yeast residing beyond the superficial follicle may not receive adequate ZnPT for anti-fungal effect forming the basis for skin re-colonisation. Levels entering systemic circulation from topical delivery are well below toxic thresholds, however the elevated zinc levels within the viable epidermis warrants further investigation. Strategies to improve formulation design can be broadly classified as influencing 1) topical delivery, 2) therapeutic bioactivity, 3) skin mildness, and 4) sensory attributes. Successful SD treatment ultimately requires formulations that can balance efficacy, safety, and consumer appeal.