Table of ContentsView AllTable of ContentsYour First Heat RashRecurring Heat RashTriggersPreventionHeat Rash Not Improving
Table of ContentsView All
View All
Table of Contents
Your First Heat Rash
Recurring Heat Rash
Triggers
Prevention
Heat Rash Not Improving
The human body has millions of eccrine sweat glands that can excrete liters of sweat daily, especially when it’s hot and humid outside. High temperatures and muggy weather increase the incidence of heat rash because people increasingly sweat in these conditions. Anything that causes eccrine duct blockages and prevents sweat from reaching the skin’s surface can cause heat rash.
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First Time With Heat Rash: Why?
Heat rashis most common in hot, humid weather. Many people who live in areas with seasonal weather changes get heat rash every year when it gets hotter in the spring and summertime. Someone who doesn’t usually get heat rash may get it for the first time when vacationing in a tropical location with extremely hot ambient temperatures and high humidity levels.
Anytime you sweat in conditions that trap heat next to your skin, the greater your odds of getting aheat rash. For example, some people may get heat rash for the first time if they start working out harder than usual and sweat more at the gym or while doing high-intensity physical activity outside.
Wearing non-breathable fabrics that trap sweat and prevent evaporation can cause heat rash if an eccrine sweat gland or duct gets blocked or clogged. Slathering your skin with heavy lotions or thick, physical sunblocks that are comedogenic (block skin pores) may cause heat rash if they trap perspiration.
If you have never had heat rash before but have one now, take inventory of anything that’s changed with your skin care regimen or daily routine, and discontinue using any products or clothing that may be blocking your pores on hot, humid days or while doing vigorous exercise.
Fevers, Bed Rest, and Medication Can Cause Heat RashYour first experience with a heat rash may occur when you are sick in bed and experience a fever or cold sweats (perspiring and being cold at the same time). Heavy bedding or nightclothes can trap the sweat against your skin, causing a heat rash.
Fevers, Bed Rest, and Medication Can Cause Heat Rash
Your first experience with a heat rash may occur when you are sick in bed and experience a fever or cold sweats (perspiring and being cold at the same time). Heavy bedding or nightclothes can trap the sweat against your skin, causing a heat rash.
This photo contains content that some people may find graphic or disturbing.See PhotoReproduced with permission from ©DermNetdermnetnz.org2023.
This photo contains content that some people may find graphic or disturbing.See Photo
This photo contains content that some people may find graphic or disturbing.
Reproduced with permission from ©DermNetdermnetnz.org2023.
What Causes Recurrent Heat Rash?
Thick lotions or tight, non-breathable clothing can cause recurrent heat rash anywhere that sweat repeatedly gets trapped under the skin’s surface.
Heat rash commonly occurs where there’s skin-to-skin contact on the body, such as the folds of skin under the breasts, armpit (axilla), groin area, elbow/knee joint creases, or anywhere on the body that sweat doesn’t evaporate quickly.
Typically, perspiration travels to the skin’s surface through eccrine ducts and evaporates or drips away from sweat pores once it’s above the outermost layer of skin (the stratum corneum). However, beads of sweat can get trapped beneath the skin’s surface and create little fluid-filled sacs (vesicles) that look like tiny raised bumps if these eccrine ducts become clogged or blocked. Anything that causes perpetual sweat gland blockage (occlusion) can cause recurrent heat rash.
Can You Get Heat Rash in Wintertime? Yes.
Mild to Severe Heat Rash Triggers
Slightly warm temperatures and conditions that moderately increase perspiration can trigger mild heat rash. Heat waves (i.e., numerous days of abnormally high temperatures) that cause excessive perspiration can be a severe heat rash trigger.
Anything that causes the sweat glands to be blocked during periods of high temperatures and humidity can cause heat rash, including:
Record-breaking heat days, which occur with increasing frequency around the globe, cause an uptick in heat-related illnesses like heat rash, heat cramps, heat exhaustion, and heatstroke.
How to Stay Ahead of Heat Rash
Keeping your skin cool and dry is the best way to avoid heat rash.
Ways to deal with heat rash include:
Heat rash should improve on its own in a few days, but it can last up to three weeks. Because heat rash is a self-limiting skin condition, meaning it usually resolves on its own without treatment once miliaria-causing triggers (e.g., heat, humidity) have subsided or been removed, if heat rash is not improving, contact a healthcare professional.
Summary
Anyone can get heat rash, but it’s more likely to occur in hot, humid weather that increases perspiration and the odds of a sweat gland getting clogged or blocked.
10 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Palaniappan V, Sadhasivamohan A, Sankarapandian J, Karthikeyan K.Miliaria crystallina.Clinical and Experimental Dermatology. 2023;48(5):462-467. doi:10.1093/ced/llad032Baker LB.Physiology of sweat gland function: The roles of sweating and sweat composition in human health.Temperature. 2019;6(3):211-259. doi:10.1080/23328940.2019.1632145Nichols AW.Heat-related illness in sports and exercise.Curr Rev Musculoskelet Med. 2014;7(4):355-365. doi:10.1007/s12178-014-9240-0Williams ML.Global warming, heat-related illnesses, and the dermatologist.International Journal of Women’s Dermatology. 2021;7(1):70-84. doi:10.1016/j.ijwd.2020.08.007Marx W, Haunschild R, Bornmann L.Heat waves: A hot topic in climate change research.Theor Appl Climatol. 2021;146(1-2):781-800. doi:10.1007/s00704-021-03758-yFamily Doctor.Heat rash.Healthdirect.Heat rash.Shin M, Halaki M, Swan P, Ireland A, Chow CM.The effects of fabric for sleepwear and bedding on sleep at ambient temperatures of 17°C and 22°C. NSS. Published online April 2016:121 doi:10.2147/NSS.S100271Hyde T, Albarracín D.Record-breaking heat days disproportionately influence heat perceptions.Sci Rep. 2023;13(1):17011. doi:10.1038/s41598-023-41317-9NHS.Heat rash (prickly heat).Additional ReadingDanzig RM, Raunig JM, Acholonu CJ.Exertional heat illness—from identifying heat rash to treating heat stroke.Pediatr Ann. 2024;53(1). doi:10.3928/19382359-20231113-04
10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Palaniappan V, Sadhasivamohan A, Sankarapandian J, Karthikeyan K.Miliaria crystallina.Clinical and Experimental Dermatology. 2023;48(5):462-467. doi:10.1093/ced/llad032Baker LB.Physiology of sweat gland function: The roles of sweating and sweat composition in human health.Temperature. 2019;6(3):211-259. doi:10.1080/23328940.2019.1632145Nichols AW.Heat-related illness in sports and exercise.Curr Rev Musculoskelet Med. 2014;7(4):355-365. doi:10.1007/s12178-014-9240-0Williams ML.Global warming, heat-related illnesses, and the dermatologist.International Journal of Women’s Dermatology. 2021;7(1):70-84. doi:10.1016/j.ijwd.2020.08.007Marx W, Haunschild R, Bornmann L.Heat waves: A hot topic in climate change research.Theor Appl Climatol. 2021;146(1-2):781-800. doi:10.1007/s00704-021-03758-yFamily Doctor.Heat rash.Healthdirect.Heat rash.Shin M, Halaki M, Swan P, Ireland A, Chow CM.The effects of fabric for sleepwear and bedding on sleep at ambient temperatures of 17°C and 22°C. NSS. Published online April 2016:121 doi:10.2147/NSS.S100271Hyde T, Albarracín D.Record-breaking heat days disproportionately influence heat perceptions.Sci Rep. 2023;13(1):17011. doi:10.1038/s41598-023-41317-9NHS.Heat rash (prickly heat).Additional ReadingDanzig RM, Raunig JM, Acholonu CJ.Exertional heat illness—from identifying heat rash to treating heat stroke.Pediatr Ann. 2024;53(1). doi:10.3928/19382359-20231113-04
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Palaniappan V, Sadhasivamohan A, Sankarapandian J, Karthikeyan K.Miliaria crystallina.Clinical and Experimental Dermatology. 2023;48(5):462-467. doi:10.1093/ced/llad032Baker LB.Physiology of sweat gland function: The roles of sweating and sweat composition in human health.Temperature. 2019;6(3):211-259. doi:10.1080/23328940.2019.1632145Nichols AW.Heat-related illness in sports and exercise.Curr Rev Musculoskelet Med. 2014;7(4):355-365. doi:10.1007/s12178-014-9240-0Williams ML.Global warming, heat-related illnesses, and the dermatologist.International Journal of Women’s Dermatology. 2021;7(1):70-84. doi:10.1016/j.ijwd.2020.08.007Marx W, Haunschild R, Bornmann L.Heat waves: A hot topic in climate change research.Theor Appl Climatol. 2021;146(1-2):781-800. doi:10.1007/s00704-021-03758-yFamily Doctor.Heat rash.Healthdirect.Heat rash.Shin M, Halaki M, Swan P, Ireland A, Chow CM.The effects of fabric for sleepwear and bedding on sleep at ambient temperatures of 17°C and 22°C. NSS. Published online April 2016:121 doi:10.2147/NSS.S100271Hyde T, Albarracín D.Record-breaking heat days disproportionately influence heat perceptions.Sci Rep. 2023;13(1):17011. doi:10.1038/s41598-023-41317-9NHS.Heat rash (prickly heat).
Palaniappan V, Sadhasivamohan A, Sankarapandian J, Karthikeyan K.Miliaria crystallina.Clinical and Experimental Dermatology. 2023;48(5):462-467. doi:10.1093/ced/llad032
Baker LB.Physiology of sweat gland function: The roles of sweating and sweat composition in human health.Temperature. 2019;6(3):211-259. doi:10.1080/23328940.2019.1632145
Nichols AW.Heat-related illness in sports and exercise.Curr Rev Musculoskelet Med. 2014;7(4):355-365. doi:10.1007/s12178-014-9240-0
Williams ML.Global warming, heat-related illnesses, and the dermatologist.International Journal of Women’s Dermatology. 2021;7(1):70-84. doi:10.1016/j.ijwd.2020.08.007
Marx W, Haunschild R, Bornmann L.Heat waves: A hot topic in climate change research.Theor Appl Climatol. 2021;146(1-2):781-800. doi:10.1007/s00704-021-03758-y
Family Doctor.Heat rash.
Healthdirect.Heat rash.
Shin M, Halaki M, Swan P, Ireland A, Chow CM.The effects of fabric for sleepwear and bedding on sleep at ambient temperatures of 17°C and 22°C. NSS. Published online April 2016:121 doi:10.2147/NSS.S100271
Hyde T, Albarracín D.Record-breaking heat days disproportionately influence heat perceptions.Sci Rep. 2023;13(1):17011. doi:10.1038/s41598-023-41317-9
NHS.Heat rash (prickly heat).
Danzig RM, Raunig JM, Acholonu CJ.Exertional heat illness—from identifying heat rash to treating heat stroke.Pediatr Ann. 2024;53(1). doi:10.3928/19382359-20231113-04
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