When did sweat become such a badge of shame? Is it because there is often an accompanying odour? Or perhaps, the stains on clothing are far too unbearable to see? It seems we have conditioned ourselves to accept only a narrow range of appropriate sweat, time to sweat, and area of our bodies that can sweat. Perhaps if we understood the role of sweat, how it forms and how we can mitigate some of the unpleasant associations, we can get back to just sweating it out.
What is Happening When You Sweat?
Sweating is one of our most efficient methods to cool the body; enabling dissipation of heat through the evaporation of sweat, helping us adapt to different climates and ensuring that our internal organs don’t overheat. Eccrine and apocrine glands produce and secrete sweat, which is normally composed of 99% water. The kidney is the primary site for electrolyte re-balancing (see our previous post on kidney function) and perspiration plays an important role in electrolyte excretion. Sodium, chloride and other electrolytes are excreted as we sweat in addition to some cellular waste. An average healthy adult can produce 0.5L of sweat/hr while those with higher thermoregulatory requirements (e.g. athletes or those living in a hot climate) can increase the volume of sweat produced (up to 3-4L/hr) while still conserving key electrolytes.
Signals to Sweat:
The sympathetic nervous system regulates the sweating reflex with external stimuli (i.e. elevated external temperatures) resulting in an increased internal or mean body temperature which can cause an increase in sweat and blood circulation. The nerve fibers entwining the eccrine sweat glands carry sympathetic signals from the brain causing the release of acetylcholine to activate muscarinic receptors on the sweat glands. This process also results in “active cutaneous vasodilation” which is a fancy way of saying improved blood flow to the skin.. This response has been shown to decrease with aging, which may explain some of the thermoregulatory changes as we age such as the increased risk of hypothermia for the elderly. Apocrine glands, activated at puberty secrete sweat that is composed of fatty acids and protein in addition to water and electrolytes. The apocrine gland stimulation contributes to more emotional based sweat responses such as stress or fear.
When Sweat Goes Wrong?
As we mentioned earlier, there is a negative association with sweat often related to “inappropriate or excessive” sweating. So why do some people sweat more than others? Hyperhidrosis (excessive sweating in localised areas) can be primarily related to overproduction by the glands.
Primary hyperhidrosis generally increases sweat from palms and soles and may include underarms or face. In order to be diagnosed with hyperhidrosis an individual must experience excessive visible sweating that has persisted for more than six months and impacts an individuals quality of life. An odour results from sweat when the secretions mix with the metabolic products of bacterial microflora present on the skin. While this is normal, the odour can be mitigated by not letting the sweat sit on the skin for excessive periods of time. Hyperhidrosis may also be secondary to metabolic dysfunction, tumour or infection. For example, the increased metabolic stress resulting from hyperthyroidism can result in excessive sweating. Excessive sweating at night can be a benign association with menopause, or it could be a sign of infections such as tuberculosis or systemic concerns such as cancer. Therefore, it is important to investigate the cause of excessive perspiration. Treatments that block the production of sweat include surgical options or the more popular botox, in which injected botulinum A toxin blocks aquaporin proteins that add water to the sweat. A Chinese study in 2008 found that acupuncture had a statistically significant effect on spontaneous hyperhidrosis compared with conventional treatments in 26 subjects.
Lack of sweat, or anhidrosis, can also be cause for concern as it may be due to improper neural stimulation, degenerative syndromes, tumours, and drugs among other causes. It is often characterised by a heat intolerance and requires thorough investigation by a healthcare professional. The simplest explanation is often associated with clogged pores blocking proper perspiration.
The War on the Pore
Pores surround hair follicles and act as conduits that enable the excretion of sweat from eccrine glands, and sebum (or oils) from sebaceous glands. The cosmetic industry had us believing that we could magically shrink or open the pore. The size of these pores is related to age, sex, sebum output, and cellular debris that can accumulate and increase the appearance of these pores. This can lead to whiteheads and acne. When we steam or apply heat we improve the permeability of the upper layer of the skin allowing for easier debridement of clogged pores as well as improved local circulation for oxygenation and healing. In fact, regular sauna treatments have been shown to have a protective effect on skin physiology and regulate sweat signals. Therefore make the most of your favourite sauna and sweat it out.
Alan M W Porter. Why do we have apocrine and sebaceous glands? J R Soc Med. 2001 May; 94(5): 236–237.
Kim BY, Choi JW, Park KC, Youn SW. Sebum, acne, skin elasticity, and gender difference - which is the major influencing factor for facial pores? Skin Res Technol. 2013 Feb;19(1):e45-53.
Kowatzki D, Macholdt C, Krull K, Schmidt D, Deufel T, Elsner P, Fluhr JW. Effect of regular sauna on epidermal barrier function and stratum corneum water-holding capacity in vivo in humans: a controlled study. Dermatology. 2008;217(2):173-80. doi: 10.1159/000137283.
Lee SJ, Seok J, Jeong SY, Park KY, Li K, Seo SJ.Facial Pores: Definition, Causes, and Treatment Options.Dermatol Surg. 2016 Mar;42(3):277-85. doi: 10.1097/DSS.0000000000000657.
Manabu Shibasaki and Craig G. Crandall Mechanisms and controllers of eccrine sweating in humans. Front Biosci (Schol Ed). 2010 Jan 1; 2: 685–696.
Miller, JL, Diseases of the Eccrine and Apocrine Sweat Glands. Dermatology, Elsevier 39, 587-602.e1
Minson CT, Holowatz LA, Wong BJ, Kenney WL, Wilkins BW. Decreased nitric oxide- and axon reflex-mediated cutaneous vasodilation with age during local heating. J Appl Physiol (1985)Nov;93(5):1644-9.
Roh, M., Han, M., Kim, D. and Chung, K. (2006), Sebum output as a factor contributing to the size of facial pores. British Journal of Dermatology, 155: 890–894. doi:10.1111/j.1365-2133.2006.07465.x
Santana-Rodríguez N, Clavo-Varas B, Ponce-González MÁ, Jarabo-Sarceda JR, Pérez-Alonso D, Ruiz-Caballero JA, Olmo-Quintana V, Atallah Yordi N,Fiuza-Pérez MD. Primary frontal hyperhidrosis successfully treated with low doses of botulinum toxin A as a useful alternative to surgical treatment. MJ Dermatolog Treat. 2012 Feb;23(1):49-51.
Wang WZ, Zhao L. Acupuncture treatment for spontaneous polyhidrosis. J Trad Chin Med 2008;28:262–263