Heat Rashes

Heat Rashes: Causes, Picture, Symptoms, Treatment And Prevention

Healthy skin is a reflection of overall wellness. A shining and glowing skin irrespective of color and free of any damage is the sign of good health.

Could anybody think of better clothing to the thousands of bodily parts than the skin? The answer is no. The skin apart from covering and protecting the body from various external conditions also has many functions.

Sweating from hard work is a sign of good skin and also good for a healthy body. Sweating maintains body temperature. Rashes can occur if sweating by heat is blocked.

Sunlight is the main source of Vitamin D but when overexposed could cause rashes. For those who believe that beauty is only skin deep and for others to have a glowing skin free of rashes continue reading.

Rashes to the skin due to heat are called Miliaria. This medical term is used to the blockages of sweat glands and causing rashes on the skin. They are mainly formed on the face and neck of the human body.

Sweat Glands:

Sweat glands are the main part of the skin which causes sweat. The blockage of the ducts in the sweat glands causes rashes.

heat rashes by sweat glands
source: Quora

Sweat glands are tubular in structure and of two types:

Types of Sweat glands:

Eccrine sweat glands:

These glands are found all over the body and are the main reason for the heat rashes.

Apocrine sweat glands:

These glands are limited to the per anal areas and armpits in humans.

Functions of sweat glands:

  • Sweat glands secrete sweat which contains water and urea. Though the urea is only 10 % of the urine secretion it is also vital in maintaining the body temperature.
  • The main electrolytes of sweat are sodium and chlorine. The sweat from the eccrine gland which is responsible for the rashes has a pH level of 4 to 6.8.
  • Sweat glands are located in the epidermis layer of the skin and also in the deep stratum layer. They are regulated by the temperature control centers in the brain.
  • Sweat ducts convey the sweat from the glands to the surface of the skin. When these ducts are blocked due to various reasons rashes occur. The ducts become clogged and the sweat cannot get to the surface of the skin causing inflammation or rash on the skin.


Heat rashes on the skin are mainly due to the heat. Heat is the energy transferred from one system to another as a result of thermal interactions.

Hot temperatures of the summer days can make anyone uncomfortable due to the unbearable heat. Due to overheating a number of heat-related illnesses occur to the humans including heat rashes.

Because of the heat, Miliaria or the heat rashes occur on the skin of the human body.


Miliaria or heat rash is a condition that occurs due to the obstruction of the sweat ducts. This obstruction is due to the excessive sweating because of the unbearable heat of the surroundings.

It affects nearly 15 % of newborn babies. And also there is no age restriction for miliaria to occur. Miliaria does not occur around hair follicles like acne.

Types of Miliaria:

Miliaria Crystallina :

This kind of heat rash appears as small, clear and superficial blisters. While bathing or friction these blisters break easily. This is the mildest form of rashes which affects the ducts on the top layer of the skin.

This form of heat rash commonly occurs to the following persons:

  • Neonates or newborn babies
  • Mostly those within one week of birth
  • Febrile persons who are suffering from fever
  • For those who have newly moved to humid and high-temperature demographical locations

Miliaria Rubra:

  • These are also smaller in size but are bumpy spots which are itchy and prickly. Hence it is also called prickly heat rashes.
  • This is formed in 30 % of persons who have moved to tropical locations,
  • Miliaria Rubra may lead to Anhidrosis in some specified areas of the body. Anhidrosis is a condition where no sweat is generated and hence becomes symptomatic with itching and stinging.
  • Anhidrosis in specified areas can last for weeks. If anhidrosis is generalized it may lead to heat exhaustion and hyperpyrexia.
  • Secondary infection is also possible with Miliaria Rubra.

Miliaria Pustolosa:

In worst and chronic recurrent cases the bumpy spots can turn into pus-filled spots. The vesicles or sacs are filled with pus and hence called pustulosis.

Miliaria Profunda:

The one happy thing about this kind of heat rash is it is not itchy but is formed in the deeper layer of the skin in the form of red or white lumps.

This is very rare and is found in persons who relapse to Miliaria Rubra.

Rashes :

The rash is a change of the human skin which affects its color, texture, and appearance. It may also cause itching which could be unbearable. The itchy rash is called allergic contact dermatitis.

heat rashes on a baby Rashes do not discriminate age or sex. Almost everyone should have experienced a rash at some point in time in their lives. Some rashes are for a very short time and some exist for a longer period of time.

The heat rashes may occur on all part of the body due to the eccrine sweat glands. But the heat rashes are more focused on the part which are exposed to heat like face, neck, and hands.

Causes Of Heat Rashes:

As per the name, the heat rashes are mainly caused by heat on the body surface. The sunlight in the morning is rich in vitamin D. This is the only natural resource of Vitamin D which is very essential for body functioning.

But when the ultraviolet or the UV rays are overexposed on the human skin it causes a lot of skin ailments including heat rashes.

Some persons may experience over sweating which takes time to evaporate. This causes the ducts or the tubular structures connecting the eccrine glands to the skin surface to be blocked.

This blockage or clogging of the ducts and the sweat glands overtime cause rashes. In severe cases itching, pricking and pain are also experienced in the rashes.

Common causes of heat rashes:

Physical activity:

Hard work involving too much physical activity, heavy or intense exercises, and any other activity which causes severe sweating cause heat rashes.


The sweating on evaporation causes the coolness of the body. But on overheating due to the hot working environment, or in humid conditions which cause overheating of the body could be the cause of heat rashes.


Fever for a prolonged time because of an underlying ailment also could cause rashes.


Obesity causes more skin to skin contact because of the large body mass. This friction due to the frequent skin contact could cause heat rashes.

Tropical climates:

Changing over to tropical climates for a long period of stay or permanently could lead to heat rashes.

Lotions & creams:

Some heavy creams and lotions applied on the skin may block the sweat glands and the ducts and could be the cause of heat rashes.


Medical Causes of heat rashes:


Occlusion is the closing of the sweat glands and the ducts due to the clogging or blocking. This is because of the following reasons:

  • Transdermal patches on the skin:

Transdermal patches are put on the skin to transmit some kind of. medicines to the bloodstream of the affected bodily part.

Occlusion clothing:

Some clothing with nylon, rayon, Kevlar or any synthetics has more risk of heat rashes.

Also, training and defense dresses could cause heat rashes.

Acclimatization defects:

Lack of acclimatization or adjusting to the change of climate, altitude, temperature, humidity, and others can also cause heat rashes.

Morvan Syndrome:

Morvan syndrome is the defect in the CNS or the central nervous system disorders which causes insomnia, weight loss, hallucinations, pain, hyperhidrosis, and other issues could cause heat rashes.

UV radiation:

UV or ultraviolet radiation in some cases cause heat rashes.


Certain intake of drugs can cause heat rashes.

  • Bethanechol, Clonidine,& Neostigmine:

These drugs which promote sweat cause heat rashes.

  • Isotretinoin:

This medicine affects follicular differentiation and causes miliaria.

  • Doxorubicin or Erythropoietin:

Miliaria crystalline has been found when these drugs are administered into the human body.


  1. PHA or pseudohypoaldosteronism is a heterogeneous group of disorders of electrolyte metabolism characterized by an apparent state of renal tubular unresponsiveness of resistance to the action of aldosterone.
  2. PHA is manifested by metabolic acidosis, hyperkalemia, and a normal glomerular filtration rate.
  3. PHA causes excessive loss of salt through the eccrine secretions and is associated with repeated episodes of pustular miliaria rubra.


Some bacteria like Staphylococcus epidermidis and Staphylococcus aureus are associated with miliaria. They form biofilms and block the sweat glands and hence play a role in the pathogenesis of miliaria.

Causes of Heat rashes on babies:

The newborn babies are the most affected ones due to the heat rashes. The new environment for the babies and the immature development of the bodily parts are the major reasons.

Immature sweat ducts:

The sweat ducts of the newborn born babies are not fully developed. It could easily be ruptured causing the perspiration trapping beneath the skin.

This is more common in the first week of birth. This is because of the following reasons:

  • Keeping the baby in the incubator which warms the infant
  • Dressing the baby too warm
  • When the infant suffers from fever
  • Excessive sweating
  • Creases on the skin

Symptoms Of Heat Rashes:

Symptoms of heat rashes are the rashes which can occur all over the body and in some cases localized. The symptoms are according to the characteristics of the rashes.

Occluded sweat glands with trapped sweat give rise to tiny water bumps

Salt which is the main content of sweat can cause potent skin irritant and skin rashes.

The different types of rashes:

  • Blisters
  • Pimples
  • Itchiness in rashes
  • Raised red welts
  • Discolored skin mainly red in color
  • Discolored blotches which are mainly red in color
  • Ring-shaped rashes
  • Slightly raised or lacy patch of skin]
  • Pus-filled, crusty swellings
  • Thick and leathery skin patch
  • Scaly or flaky skin patch
  • Oozing areas which become crusty

The different parts where heat rashes occur in the body:

  • Neck
  • Back
  • Abdomen
  • Face
  • Groin
  • Buttocks
  • Elbow folds
  • Under the breasts

When the rashes are severe for the following reasons it is time to see a doctor.

  • Rashes on the skin for a long period of time
  • Increased size of the heat rashes
  • The severity of the color change of the rashes
  • Unbearable pain or swelling
  • Increased warmth around the rash affected area
  • Swollen lymph nodes in the armpit, neck or groin
  • Frequent fever or chills
  • Pus coming out from the lesions
  • Difficulty in breathing
  • Frequent fever which lasts for a prolonged time
  • Severe head or neck pain
  • Dizziness or confusion
  • Swelling of the face or extremities
  • Tightness or itchiness or soaring in the throat for a considerable period of time
  • Repeated diarrhea or vomiting

Diagnoses Of Heat Rashes:

Since heat rashes are easily visible to the naked eye it could be self-diagnosed and treatment is taken. But in some cases where it persists with many symptoms, it is time to diagnose the heat rashes.

Clinical diagnoses:

The doctor can question the change of environment, exposure to heat, physical activity among others to evaluate the reasonableness of rashes.

The doctor could also perform a simple diagnostic test by inserting a needle to rupture the blister and examine the fluid or sweat accumulated there.

Microscopic Examinations:

The skin scrapings are collected to conduct microscopic examinations.

Skin culture Test:

Depending on the cause of the rashes a skin culture test can also be done.


Biopsy of the skin could be advised to rule out the other conditions that are similar to that of heat rashes like toxic, neonatorum, neonatal cephalic, erythema, candidiasis, Grover’s disease, pustulosis among others.

Swab Test:

To rule out the possibility of the secondary infections swab test can be done by the doctors.

Patch Test:

In some cases, patch tests are conducted to eliminate the possibility of any allergic reactions to substances applied on the skin.

Blood tests:

Rashes may cause stress to some patients and hence blood tests are conducted to evaluate the development of heat stress syndrome.

Treatment Of Heat Rashes:

Heat rashes are mainly due to the surrounding hot conditions. Once you move to the cooler environment this could be recovered uneventfully. Prevention is the best treatment as far as heat rashes are concerned.

Common home treatments:

  • Shifting to cooler environments
  • Keeping the sleeping area well ventilated and cool
  • Avoiding tight-fitting clothes
  • Choose the clothing as per the fiber which suits your body
  • Try to be in air-conditioned rooms or under a fan with good circulation of air
  • Avoid overdressing in any climate. Cotton and light clothing will save the skin of rashes.
  • Limiting physical activities in hotter environments
  • Washing the affected areas followed by gentle drying
  • To be hydrated at all times and never be dehydrated at any point in time
  • Avoiding all kinds of plastic covered bedding or other accessories

Treatment of heat rashes by proper diet:

Food habits coupled with proper lifestyle could be a safe treatment option for heat rashes. The right foods to eat and to avoid are the key to the natural remedy for heat rashes.

Foods to avoid:

For any ailment, the foods to be avoided are best known to the sufferer of the ailment. Over time the awareness in eating which causes the increase of the rashes could be known. This is the vital element in avoiding the foods which could differ from person to person.

Most common foods which are not suited not only for rashes but for many other ailments are the following ones:

  • Processed foods:

Many processed foods contain additives to prolong the period of usage and also dyes to enhance the color of the food. These not only cause various ailments but are allergic to rashes as well.

  • Fried Foods:

Fried foods are the worst enemy of many diseases across the world. The oil and many ingredients in the fried foods cause inflammation and thus increasing the rashes.

  • Conventional dairy foods:

Some people are allergic to conventional dairy foods and hence avoid them to reduce the heat rashes.

Food to reduce heat rashes:

Foods which are rich in certain ingredients which reduce the rashes because of heat could be taken for a better living.

  • Organic foods:

Switching to organic foods is the order of the day. The fewer toxins and chemicals reduce and heal the heat rashes.

  • Beta-carotene rich foods:

Researchers have shown that beta-carotene improves resistances to rashes triggered by the sun. Eating beta carotene-rich foods could control rashes.

  • Inflammation-reducing foods:

Chia seeds and flax seeds reduce systematic inflammation. This causes a reduction in rashes symptoms.

  • Choosing the right oil for food;

The oil is the main ingredient of the food that could help in healing and reducing the ill effects of rashes.

Oils which are not heated above 129 degrees during pressing is suitable for reducing rashes. Olive and coconut oil are the best choices.2

  • Protein:

Protein is essential for the proper functioning of the human body. Clean lean protein helps the immune system and guards against infections that cause rashes.

Medical treatments for heat rashes:

Medical treatments for heat rashes depends on the severity of the rashes and also the patient’s allergic tolerance to the medicines.

OTC Medicines:

OTC or over the counter medicines are easily available for the treatment of heat rashes. Tropical creams can be applied to the affected parts for treatment.

  • Tropical creams:

There are two types of topical creams.

Steroid tropical creams:

Hydrocortisone is one steroid topical cream which is commonly used to treat heat rashes. This is avoided for long-term use because it causes thinning of the skin.

Non-steroidal tropical creams:

Patients who do not absorb the steroid topical creams to penetrate their skin or the affected areas use non-steroidal topical creams.

  • Soothing lotions:

Skin-soothing lotions like calamine lotions could be applied to reduce the effects of rashes.

  • Antibiotics and Anti-inflammatory drugs:

In the case of secondary infections of the rashes antibiotics and anti-inflammatory drugs are administered with the supervision of doctors.

  • Supplements:

Supplements which are rich in the following essential ingredients could be taken to reduce rashes;

  • Vitamin C
  • Quercetin
  • Detoxification and alkalizing supporting ingredients
  • Polyphenols

Treatment of infants for heat rashes:

Newborn babies and infants are the worst affected by heat rashes. This can be prevented and treated by the following ways:

  • Keep the baby in a cool atmosphere
  • Make the children play in shades in the time of hot temperatures
  • Babies less than six months should be kept out of direct sunlight
  • In case of taking infants out on a sunny day apply a sunscreen lotion of 30 + SPF
  • Cover the whole baby’s body with light cotton dresses
  • A cool shower before sleep

Keeping the skin free of heat rashes or of any other kind of damages to it is very important. This is because it is the only clothing available to thousands of bodily parts.

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