Why does sweat lead to the development of itch in atopic dermatitis?

Sweating plays an important role in maintaining temperature homeostasis in humans. However, under certain circumstances, sweat can cause itching. For example, when excessive sweat accumulates on the skin surface for a long period, miliaria can develop and cause itching. Subjects with dermatoses, such as atopic dermatitis (AD), suffer from itch when exposed to heat or psychological stresses, which are also known perspiration stimuli. Recently, some mechanisms of sweat-induced itch have been revealed. For instance, attenuated sweating ability is observed in subjects with AD, causing heat retention, skin dryness, and high susceptibility to itch. Furthermore, the decreased tight junction of the sweat gland in AD leads to sweat leakage in the dermis, which could be designated as a "sweat endocrine response" and may be the cause of tingling itch during sweating. Additionally, metabolomic analysis of sweat from patients with AD revealed that glucose concentration in sweat increases according to disease severity. Sweat with elevated glucose concentration retards the recovery of the damaged skin barrier and may promote itching. This viewpoint essay outlines the relationship between sweat and itch based on recent evidence.

Transcriptome Profiling of Anhidrotic Eccrine Sweat Glands Reveals that Olfactory Receptors on Eccrine Sweat Glands Regulate Perspiration in a Ligand-Dependent Manner.

Sweat maintains systemic homeostasis in humans. Although sweating disorders may cause multifaceted health problems, therapeutic options for sweat disorders have not yet been established. To gain new insight into the mechanism underlying the regulation of perspiration, we compared eccrine sweat gland transcriptomes from hidrotic and anhidrotic lesions from patients with anhidrosis and found out that olfactory receptors were expressed differentially in anhidrotic and hidrotic eccrine sweat glands. We then confirmed OR51A7 and OR51E2 expression in human eccrine sweat glands by in situ hybridization and immunohistochemistry. An alkaline phosphatase-TGFα shedding assay revealed that ß-ionone activates G-proteins through OR51A7 or OR51E2. The effect of topically applied ß-ionone on sweating was examined with the quantitative sudomotor axon reflex test, which showed that responses to ß-ionone differed between sexes. Topical ß-ionone attenuated female sweating and augmented male sweating. Taken together, this study suggests that olfactory receptors expressed in eccrine sweat glands may regulate sweating in response to odorous ligands on the basis of sex. These unexpected results indicate that olfactory receptors may modulate sweating and that olfactory receptor modulators may contribute to the management of sweat disorders.

Cost-of-illness study for axillary hyperhidrosis in Japan.

The prevalence of primary axillary hyperhidrosis in Japan is 5.75% (males, 6.60%; females, 4.72%) in the population aged 5-64 years. No study on comprehensively evaluated direct medical costs, hygiene product costs, and productivity loss in axillary hyperhidrosis patients has been published in Japan. The aim of this study was to estimate the cost of illness for axillary hyperhidrosis in Japan by conducting a nationwide insurance claims database analysis and a cross-sectional Web-based survey. Among patients diagnosed with primary axillary hyperhidrosis at least once between November 2012 and October 2019, health insurance receipt data of 1447 patients were analyzed. A cross-sectional Web-based survey was conducted on 321 patients aged 16-59 years with axillary hyperhidrosis to calculate hygiene product costs and productivity loss using a Work Productivity and Activity Impairment questionnaire. Furthermore, nationwide estimation was performed for the hygiene product costs and productivity loss based on the number of patients estimated from the prevalence. The annual direct medical costs per axillary hyperhidrosis patient were ¥91 491 in 2016, ¥93 155 in 2017, and ¥75 036 in 2018. In all of these years, botulinum toxin type A injection accounted for approximately 90% of the total costs. The annual total cost of hygiene products per axillary hyperhidrosis patient was ¥9325. The overall work impairment (%) of working patients with axillary hyperhidrosis was 30.52%, and its monthly productivity loss was ¥120 593/patient. The activity impairment (%) of full-time housewives with axillary hyperhidrosis was 49.05% and its monthly productivity loss was ¥176 368/patient. The annual hygiene product cost based on the nationwide estimation was ¥24.5 billion and the monthly productivity loss was ¥312 billion. The significant cost associated with axillary hyperhidrosis was clarified. If out-of-pocket expenses for treatments not covered by health insurance are included in the estimation, the cost will further increase.

Treatment of Severe Dermatitis, Multiple Allergies, and Metabolic Wasting With Dupilumab.

This case report describes a woman with severe dermatitis, multiple allergies, and metabolic wasting syndrome.

[Case of acute generalized exanthematous pustulosis caused by Kerorin].

A 78-year-old woman visited a local clinic because of cough and fever, and was prescribed levofloxacin, carbocisteine, and cold medicine (salicylamide, acetaminophen, anhydrous caffeine, promethazine methylene disalicylate). The following day, erythema appeared on the trunk, and spread. Multiple pustules independent of hair follicles developed on the erythema mainly in the skin folds. Histopathological examination revealed subcorneal pustular dermatosis. The clinical course and characteristics of the rashes led to a diagnosis of acute generalized exanthematous pustulosis (AGEP). Although the administration on levofloxacin, carbocisteine, and cold medicine were discontinued, the rashes recurred. We reviewed the patient's history, and found that she had a history of taking the over-the-counter drug Kerorin, and had taken a dose of Kerorin on the day before the first examination and before the recurrence. The ingestion of Kerorin was regarded as an incidental oral administration test, which was positive. Thus, oral administration tests with Kerorin and its ingredients acetylsalicylic acid and anhydrous caffeine were positive, leading to a diagnosis of AGEP caused by Kerorin.

A case of pneumatosis cystoides intestinalis in a patient with polymyositis and interstitial pneumonia.

We report the case of a 49-year-old man who presented with pneumatosis cystoides intestinalis associated with polymyositis and interstitial pneumonia. Three months after the administration of prednisolone and cyclosporine, he noticed mild abdominal distension, and a radiographic examination showed intraperitoneal free gas and intramural gas, suggestive of pneumatosis cystoides intestinalis (PCI). Additional treatment with a combination of doxycycline and high-dose oxygen therapy was effective in relieving the clinical symptoms and reducing the intramural gas.