The impact of different hair-removal behaviours on the biophysical and biochemical characteristics of female axillary skin

Objective

The impact of hair removal on the biophysical and biochemical characteristics of human axillary skin is not fully understood. This study investigated the effect of different hair‐removal techniques on biophysical parameters and the concentrations of key inflammatory biomarkers in the axillae of female Thai subjects. Axillary hair was removed by shaving, plucking or waxing.

Methods

Following a 2‐week washout phase without hair removal, subjects underwent visual assessment for erythema and skin dryness in one (randomized) axilla, then, hair was removed from the axilla by shaving, plucking or waxing according to each subject’s established habit. Erythema and dryness were assessed again 30 min after hair removal, and buffer scrubs collected from depilated and non‐depilated axillae and analysed for inflammatory cytokines; after a further 48 h, erythema, dryness and post‐inflammatory hyperpigmentation (PIHP) were assessed in the depilated axilla. Biophysical assessments (skin hydration, barrier integrity, elasticity and roughness) were made in depilated and non‐depilated axillae.

Results

All three hair‐removal techniques induced an increase in axillary erythema and skin dryness. Shaving was associated with significantly less erythema (P < 0.01), but significantly greater skin dryness (P < 0.05) versus the other techniques 30 min after hair removal. There were no between‐technique differences in PIHP or biophysical parameters. Interleukins IL‐1α and IL‐1RA concentrations increased, and IL‐8 concentration decreased following hair removal by each technique.

Conclusion

This is the first study to identify the principal cytokines associated with the inflammatory process triggered by axillary hair removal. A single hair‐removal treatment did not appear to induce PIHP or further biophysical changes to the skin.

The diversity and abundance of fungi and bacteria on the healthy and dandruff affected human scalp

Dandruff is a skin condition that affects the scalp of up to half the world's population, it is characterised by an itchy, flaky scalp and is associated with colonisation of the skin by Malassezia spp. Management of this condition is typically via antifungal therapies, however the precise role of microbes in the aggravation of the condition are incompletely characterised. Here, a combination of 454 sequencing and qPCR techniques were used to compare the scalp microbiota of dandruff and non-dandruff affected Chinese subjects. Based on 454 sequencing of the scalp microbiome, the two most abundant bacterial genera found on the scalp surface were Cutibacterium (formerly Propionibacterium) and Staphylococcus, while Malassezia was the main fungal inhabitant. Quantitative PCR (qPCR) analysis of four scalp taxa (M. restricta, M. globosa, C. acnes and Staphylococcus spp.) believed to represent the bulk of the overall population was additionally carried out. Metataxonomic and qPCR analyses were performed on healthy and lesional buffer scrub samples to facilitate assessment of whether the scalp condition is associated with differential microbial communities on the sampled skin. Dandruff was associated with greater frequencies of M. restricta and Staphylococcus spp. compared with the healthy population (p<0.05). Analysis also revealed the presence of an unclassified fungal taxon that could represent a novel Malassezia species.

Functional characterisation of a SNP in the ABCC11 allele - effects on axillary skin metabolism, odour generation and associated behaviours

BACKGROUND

A single nucleotide polymorphism (SNP), 538G→A, leading to a G180R substitution in the ABCC11 gene results in reduced concentrations of apocrine derived axillary odour precursors.

OBJECTIVE

Determine the axillary odour levels in the SNP ABCC11 genotype variants and to investigate if other parameters associated with odour production are affected.

METHODS

Axillary odour was assessed by subjective quantification and gas chromatography headspace analysis. Metabolite profiles, microbiome diversity and personal hygiene habits were also assessed.

RESULTS

Axillary odour in the A/A homozygotes was significantly lower compared to the G/A and G/G genotypes. However, the perception-based measures still detected appreciable levels of axillary odour in the A/A subjects. Metabolomic analysis highlighted significant differences in axillary skin metabolites between A/A subjects compared to those carrying the G allele. These differences resulted in A/A subjects lacking specific volatile odourants in the axillary headspace, but all genotypes produced odoriferous short chain fatty acids. Microbiomic analysis revealed differences in the relative abundance of key bacterial genera associated with odour generation between the different genotypes. Deodorant usage indicated a high level of self awareness of axillary odour levels with A/A individuals less likely to adopt personal hygiene habits designed to eradicate/mask its presence.

CONCLUSIONS

The SNP in the ABCC11 gene results in lower levels of axillary odour in the A/A homozygotes compared to those carrying the G allele, but A/A subjects still produce noticeable amounts of axillary odour. Differences in axillary skin metabolites, bacterial genera and personal hygiene behaviours also appear to be influenced by this SNP.

Therapeutic implications of a selective alpha7 nicotinic receptor abnormality in schizophrenia

A convergence of preclinical pharmacology, and human autopsy and genetic data support the existence of reduced expression and function of the alpha7 nicotinic receptor in patients with schizophrenia. The alpha7 nicotinic receptor is a member of a family of ligand-gated ion channels. The alpha7 nicotinic receptor may play an essential role in auditory sensory gating and voluntary smooth pursuit eye movements, two psychophysiological functions that are abnormal in patients with schizophrenia and closely related unaffected biological relatives. Diminished expression or function of the alpha7 nicotinic receptor in schizophrenia has stimulated consideration of selective full or partial alpha7 nicotinic receptor agonists as possible therapeutic interventions for this disorder. Further, the availability of positive allosteric modulators of nicotinic receptors that can improve the efficiency of transduction of the acetylcholine signal and prevent the rapid desensitization of the receptor should encourage these novel treatment approaches (e.g., galantamine).