About heat rash (miliaria) The causes and mechanisms of heat rash (miliaria) Symptoms and illnesses similar to heat rash (miliaria) Prevention and treatment methods for heat rash (miliaria) in adults, by age group. <By Age Group> Prevention and Treatment Methods for Heat Rash in Children (Infants) <By Age Group> How to Prevent and Treat Baby Heat Rash Q&A explaining common questions and concerns about heat rash (miliaria) Heat rash (miliaria), which develops rapidly due to excessive sweating, is a common ailment. This article, supervised by a dermatologist, provides a detailed explanation of how it develops, the different types it comes in, and other conditions that resemble it, including its causes, symptoms, and prevention and treatment methods for different age groups. About heat rash (miliaria) Heat rash, also written as "miliaria," appears rapidly in response to excessive sweating, such as in high fever or hot, humid environments. Depending on which part of the sweat gland the sweat accumulates in, heat rash (miliaria) can be classified into the following three types. Crystalline miliaria When sweat ducts become blocked within or just below the stratum corneum, small blisters (vesicles) a few millimeters in diameter form. They do not cause redness or itching and disappear within a day to a few days. They commonly occur on the faces of newborns, but can also occur in adults during fever or other illnesses. miliaria rubra It frequently occurs in hot and humid environments, in obese individuals, those with hyperhidrosis, and in infants. Sweat ducts become blocked within the epidermis, resulting in small, red papules (raised skin bumps) 1-2 mm in size. The degree of itching varies, but sometimes it can be very intense. It commonly appears on the trunk, the backs of the elbows and knees, the neck, and the armpits. It is more common in children, and scratching can lead to eczema-like symptoms and chronic itching. In severe cases, bacterial infection can occur. deep hives If you repeatedly experience miliaria rubra, you may develop numerous pale, non-itchy papules when you sweat. This is miliaria profundus, where the sweat ducts are blocked between the epidermis and dermis. Because sweat cannot escape the body, if it occurs over a wide area, the body's temperature regulation function will be impaired, and there is a risk of heatstroke, so caution is necessary. Areas prone to heat rash (miliaria) Face / Neck / Torso / Elbows Back of the knee / underarm In addition, they are more likely to occur in situations where you sweat a lot, such as when using compresses, bandages, casts, adhesive bandages, or wearing clothing that doesn't breathe well. If it worsens Impetigo This is what is commonly known as "impetigo." Scratching red miliaria can lead to bacterial (Staphylococcus aureus) infection, causing pus formation and resulting in impetigo. The red papules turn into blisters (vesicles), which then burst, causing erosions (peeling of the skin). The contents of the vesicles, which contain bacteria, "spread" to surrounding areas and distant parts of the body, causing new blisters to form. Multiple sweat gland abscesses It often follows heat rash in children and is commonly called "heat rash followed by prickly heat." Painful, red, hard, raised bumps (red nodules) can be seen on the head, face, back, and buttocks. The causes and mechanisms of heat rash (miliaria) First, let's explain how we sweat. Human skin has sweat glands all over the body, and the sweat secreted by the sweat glands travels through sweat ducts and comes out onto the body surface through sweat pores (Figure: Normal). When the temperature rises or exercise causes heat to build up inside the body, sweat is secreted. Sweat lowers body temperature through the heat of vaporization that occurs when the water evaporates from the body surface, thus regulating body temperature.Heat rash (miliaria) occurs when excessive sweating disrupts the sweat ducts, causing them to temporarily become clogged with sweat and preventing it from being easily expelled from the skin. Symptoms and illnesses similar to heat rash (miliaria) There are other skin conditions that present with symptoms similar to heat rash (miliaria). Some of the most common are listed below. Hidradenitis suppurativa This is a purulent disease that can be found in areas such as the armpits, groin, perineum, buttocks, and under the breasts. It is most common in adolescent and young adult women. Multiple folliculitis This is a condition where bacteria infect the hair follicles, causing inflammation. It can occur regardless of the season. Allergic contact dermatitis associated with metal allergy This is a common summer rash caused by metal in necklaces and rings dissolving in sweat and adhering to the skin. It can manifest as reddish papules (raised bumps on the skin) or small blisters (vesicles) accompanied by intense itching. sweat blisters It is also called dyshidrotic eczema. Numerous small blisters (vesicles) about 2-5 mm in diameter appear on the palms of the hands and soles of the feet, sometimes spreading to the backs of the hands and wrists. It may also be accompanied by itching. Prevention and treatment methods for heat rash (miliaria) in adults, by age group. Depending on the region, the number of people developing heat rash increases around the beginning of May. It seems that people who don't usually exercise much and don't have many opportunities to sweat are more prone to developing it when they suddenly go to a hot place or suddenly start exercising, which increases their sweating. People who work long hours in hot and humid environments should keep their skin clean by bathing or showering, and choose clothing that is breathable and absorbent. Elderly people who are bedridden need to be especially careful, as they cannot regulate their own room temperature or remove their clothing. <By Age Group> Prevention and Treatment Methods for Heat Rash in Children (Infants) Just like adults, ensure good ventilation, create a comfortable living environment, keep skin clean with baths and showers, and choose highly absorbent clothing. If you develop impetigo (contagious pyoderma), it is important to wash your hands frequently, keep your nails short, and avoid scratching your skin. When bathing, use a shower instead of a bathtub. Gently wash the affected area with lathered soap and avoid friction with nylon towels or similar items. After bathing, apply ointment to the affected area and protect it with gauze to prevent exudate from coming into contact with the surrounding area. Do not share towels or other items with others until the blisters have dried up. Impetigo is classified as a school-related infectious disease. Because it can spread to other children, do not leave it untreated and seek appropriate treatment. Make sure to cover the affected area properly with gauze or a bandage to prevent exposure. Usually, it is not necessary to keep the child home from school, but if the lesions spread extensively or if there are symptoms such as a slight fever, it may be best to keep the child home as a precaution. Also, swimming pools are prohibited until the child is completely recovered, as there is a risk of infecting others or worsening the condition. <By Age Group> How to Prevent and Treat Baby Heat Rash Crystalline miliaria is commonly seen on the faces of newborns. It usually disappears on its own within a few days, so treatment is not necessary. It is important to keep the skin clean and choose clothing and bedding that are soft, absorbent, and non-irritating to prevent it from developing. Pay close attention to the environment for newborns. Q&A explaining common questions and concerns about heat rash (miliaria) Is it okay if I only take precautions during the summer months? It can occur even in winter in environments with high temperature and humidity, causing you to sweat. Additionally, regardless of the season, be careful when you have a fever, or when wearing compresses, bandages, casts, adhesive bandages, or clothing that doesn't allow for good breathability, as these situations can cause excessive sweating. Do I absolutely have to go to the hospital? While crystallina usually disappears on its own within a few days, eliminating the need for a doctor's visit, red miliaria can lead to bacterial infections or progress to deep miliaria, requiring appropriate treatment at a hospital. What kind of treatment will be provided? In cases of miliaria rubra or miliaria profundus, if inflammation is severe, topical steroids are applied to the affected area. Furthermore, if a bacterial infection is suspected, topical antibiotics may be used, or oral antibiotics may be prescribed if the symptoms are severe.Preventing heat rash is important, so pay attention to room temperature, clothing, and bedding. Supervised by: Dr. Yuki Horiuchi, Director of Akihabara Skin ClinicAfter graduating from the Faculty of Medicine at Tokyo Women's Medical University, she worked at dermatology and cosmetic clinics in Tokyo before opening Akihabara Skin Clinic in 2007. She is a certified specialist of the Japanese Dermatological Association, a director of the Japanese Society for Medical Hair Removal, and an advisor to the A-Care Association. She is a member of the Japanese Dermatological Association, the Japanese Society for Aesthetic Dermatology, the Japanese Society for Laser Medicine, and the Japanese Society for Anti-Aging Medicine, among others. We take care to post accurate information,Please point out any incorrect information. Please submit any comments regarding medical information here. Return to the list of guides categorized by health symptoms.