Allergology International 69 (2020) 307e309

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Allergology International

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Letter to the Editor High concentrations in human sweat in association with type I to the semi-purified sweat

Dear Editor, To find bioactivity of histamine detected in sweat, we assessed concentrations of histamine to induce flare and wheal by the intra- (CholU) is characterized by pinpoint-sized dermal injection to healthy volunteers, and compared with hista- wheals with itching and/or stinging pain under sweating mine concentrations in sweat. Histamine concentrations at or conditions, including hot bathing, physical exercise and emotional higher than 100 ng/ml and 1000 ng/ml induced significant flare stress.1 The type I to sweat is proposed to be and wheal formations (Fig. 2a,b). In four patients with CholU, a pa- involved in its pathogenesis.2 Indeed, more than 60% of patients tient with AD and three controls, sweat histamine concentrations with CholU shows immediate-type skin reactions upon intradermal were higher than the minimum concentration to induce flare injection of autologous sweat, and histamine release from baso- upon intradermal injection (100 ng/ml). In one patient with phils against the semi-purified sweat antigen in histamine release CholU and one control, they were high enough even for wheal assay (HRA).2,3 Histamine released from skin mast cells also plays induction (1000 ng/ml). an important role in the development of wheals in CholU.1 In this In this study, we demonstrated that levels of histamine con- study, we examined histamine concentrations in sweat of patients centration in sweat obtained from patients with CholU were with CholU to describe a role of sweat histamine in the wheal for- much higher than those in human plasma. Such high histamine mation of CholU. concentrations in sweat were also detected in patients with AD Nine patients with CholU and 10 healthy volunteers (control) or CSU and even in healthy controls. It was associated with were recruited along with enrollment of seven patients with atopic against the semi-purified sweat antigen dermatitis (AD) and seven patients with chronic spontaneous urti- rather than the presence of specific diseases such as CholU, AD caria (CSU) (Supplementary Table 1). Following exercise for and CSU. Moreover, histamine concentrations in the sweat of 8 15e30 min, a sauna at 50 C for 10 min, a bath in hot water or subjects were higher than the minimum concentration of hista- emotional stress, sweat was collected by using a syringe from sub- mine to induce skin reactions upon intradermal injection. High jects' skin of the head/neck or the trunk/extremities. The amount of concentrations of sweat histamine may be due to the penetration histamine in sweat/plasma was measured by a high-performance of histamine which released from skin mast cells in response to liquid chromatography system.4 HRA in response to the semi- sweat antigen in the proximity of the sweat glands and ducts. purified sweat antigen was performed by using the subjects’ Indeed, it is noteworthy that sweat histamine in all nine subjects basophils as described previously.3 This study was approved by with more than 15% histamine release in response to the sweat the institutional review board of Hiroshima University Hospital antigen was higher than 25 ng/ml (Fig. 1c). However, several sub- (approval number, E-1420). jects showed high histamine concentrations in their sweat with Median histamine concentrations in sweat of patients with low basophil histamine release (5%) activity in response to CholU, AD or CSU, and healthy controls were 90.8, 30.8, 3.84 and the sweat antigen, regardless of the presence of CholU, AD or 39.7 ng/ml without significant difference (Fig. 1a). They were CSU and even in healthy controls (Fig. 1b,c, Supplementary much higher than histamine concentrations in plasma of healthy Fig. 2). Since histamine can be produced not only by skin mast subjects (n ¼ 5; mean ± SE, 0.89 ± 0.18 ng/ml). Thus, levels of sweat cells but also by epidermal keratinocytes,5 histamine released histamine concentration largely varied among individuals and from epidermal keratinocytes around the pore of sweat duct were not related to specific diseases. However, significant higher may also be stored or intermingled in sweat in a manner inde- histamine concentrations in sweat were detected in subjects with pendent from sweat allergy. In addition, the specific develop- high histamine release (>5%) against the semi-purified sweat anti- ment of flare and wheal reaction upon sweating by patients gen in HRA (sweat allergyþ) than those with low histamine release with CholU is a matter of discussion. It may be induced by a (sweat allergy-) (median, 86.8 vs 17.5 ng/ml; cut off value, 79.9 ng/ leakage of sweat with high concentration of histamine into the ml) (Fig. 1b, Supplementary Fig. 1). There was also positive correla- dermis through sweat ducts. No skin reaction should be devel- tion between histamine release from the subjects’ basophils in oped even with high histamine in sweat as long as sweat is response to the sweat antigen in HRA, and histamine concentra- retained in the sweat gland apparatus as in healthy individuals. tions in sweat (Fig. 1c). In fact, the leakage of sweat into the dermis due to the impaired tight junction has been reported in patients with AD and CholU.6

Peer review under responsibility of Japanese Society of Allergology. https://doi.org/10.1016/j.alit.2019.08.011 1323-8930/Copyright © 2019, Japanese Society of Allergology. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/). 308 Letter to the Editor / Allergology International 69 (2020) 307e309

Fig. 1. (a) Histamine concentrations in sweat of patients with CholU, AD or CSU and healthy controls. The median values of each group were 90.8, 30.8, 3.84 and 39.7 ng/ml without significant difference. (b) Histamine concentrations in sweat in the context of type I hypersensitivity to sweat (sweat allergy). The subjects whose basophils released high histamine (>5%) in response to the semi-purified sweat antigen in HRA (sweat allergyþ) showed significantly higher concentrations of sweat histamine than the subjects with low histamine release in HRA (sweat allergy-) (p ¼ 0.012). (c) The relationship of sweat histamine concentrations and histamine release in response to the semi-purified sweat antigen in HRA (using regression analysis; p < 0.05 was considered statistically significant). Histamine concentrations in sweat positively correlated with histamine release. CholU, cholinergic urticaria; AD, ; CSU, chronic spontaneous urticaria; HRA, histamine release assay.

Fig. 2. Biological activity of histamine concentration detected in sweat in reference to the size of wheals and flares induced by intradermal injection of histamine at indicated concentrations. Intradermal injections of histamine at 100 ng/ml and 1000 ng/ml or higher, but not at 10 ng/ml and 100 ng/ml or less induced significant skin reactions of flare (a) and wheal (b), respectively. Letter to the Editor / Allergology International 69 (2020) 307e309 309

Ilves et al. reported the presence of histamine in the sweat Shunsuke Takahagi, Mayumi Okamoto, Kaori Ishii, Akio Tanaka, * of patients with AD (8.67 ± 15.3 ng/ml) and healthy donors Yuhki Yanase, Michihiro Hide ± (13.0 34.1 ng/ml) collected from the back of subjects after ex- & 7 Department of Dermatology, Institute of Biomedical Health Sciences, Hiroshima ercise. The reason for the discrepancy in histamine concentra- University, Hiroshima, Japan tion between their report and ours remains unclear. The concentration of sweat histamine was not affected by the site * Corresponding author. Department of Dermatology, Institute of Biomedical & of collecting sweat and the methods of perspiration, such as Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima 734- 8551, Japan. via heat or exercise provocation (Supplementary Fig. 3). More- E-mail address: [email protected] (M. Hide). over, no decrease of histamine concentration was observed af- ter incubation at 37 C for 60 min in 8 sweat samples (Supplementary Fig. 4), implying the absence of substance decomposing histamine in sweat. Further study, exploring the References possibility of the presence of substances neutralizing histamine activity in sweat and the mechanism to condensate sweat his- 1. Fukunaga A, Washio K, Hatakeyama M, Oda Y, Ogura K, Horikawa T, et al. Cholin- tamine on the skin surface or sweat gland may explain the ergic urticaria: epidemiology, physiopathology, new categorization, and man- agement. Clin Auton Res 2018;28:103e13. large variation of histamine concentrations in sweat among 2. Takahagi S, Tanaka A, Hide M. Sweat allergy. Allergol Int 2018;67:435e41. subjects and the mechanism of wheal-and-flare formation in 3. Takahagi S, Tanaka T, Ishii K, Suzuki H, Kameyoshi Y, Shindo H, et al. Sweat an- CholU. Collectively, we demonstrated much higher levels of his- tigen induces histamine release from basophils of patients with cholinergic ur- ticaria associated with atopic diathesis. Br J Dermatol 2009;160:426e8. tamine concentration in human sweat than those in plasma in 4. Koro O, Furutani K, Hide M, Yamada S, Yamamoto S. Chemical mediators in association with sweat allergy. It may be involved in the path- atopic dermatitis: involvement of leukotriene B4 released by a type I allergic re- omechanism of CholU cooperating with the leakage of sweat action in the pathogenesis of atopic dermatitis. J Allergy Clin Immunol 1999;103: 663e70. into the dermis. 5. Shimizu K, Andoh T, Yoshihisa Y, Shimizu T. Histamine released from epidermal keratinocytes plays a role in alpha-melanocyte-stimulating hormone-induced itching in mice. Am J Pathol 2015;185:3003e10. 6. Yamaga K, Murota H, Tamura A, Miyata H, Ohmi M, Kikuta J, et al. Claudin-3 loss causes leakage of sweat from the sweat gland to contribute to the pathogenesis Appendix A. Supplementary data of atopic dermatitis. J Investig Dermatol 2018;138:1279e87. 7. Ilves T, Virolainen A, Harvima IT. Immediate wheal reactivity to autologous sweat fi Supplementary data to this article can be found online at in atopic dermatitis is associated with clinical severity, serum total and speci c IgE and sweat tryptase activity. Int Arch Allergy Immunol 2016;170:84e91. https://doi.org/10.1016/j.alit.2019.08.011. Received 19 February 2019 Conflict of interest Received in revised form 14 August 2019 The authors have no conflict of interest to declare. Accepted 27 August 2019 Available online 20 September 2019