Pictures Of Heat Rash

A note from Cleveland Clinic

Heat Rash/Prickly Heat

A heat rash, prickly heat rash or sweat rash is a group of tiny pimples or blisters on your skin caused by sweat rapped in your glands. The rash can be painful or itchy. Treat the rash at home by keeping your skin cool and dry. Contact your healthcare provider if your rash lasts longer than a week or causes severe pain or discomfort.

Overview

A heat rash is a group of tiny pimples in areas of your body that don’t get enough airflow, especially near the underarms or diaper region among infants.

What is a heat rash?

A heat rash is an area of your skin that becomes irritated because of sweat trapped in the pores and pathways (ducts) underneath your skin. Since sweat can’t leave your body, a rash forms with tiny pimples or blisters. Heat rashes are common in hot and humid climates. The rash most often develops areas of your body that don’t get enough airflow or areas where there’s skin-to-skin contact.

What are other names for a heat rash?

Heat rashes are also called:

Prickly heat rash.
Sweat rash.
Miliaria.

Who does a heat rash affect?

A heat rash can affect anyone at any age. Babies, infants and toddlers have a higher risk because their glands and ducts are still growing. They’re also usually well bundled or in multiple layers of clothing. Sweat causes heat rashes, so people who live in warm and humid climates or athletes are at a high risk as well. Heat rashes can affect people on bedrest when their clothing sits between their skin and another surface for a long period. Fever during an illness may also induce a heat rash.

How common are heat rashes?

Heat rashes affect an estimated 4% to 9% of newborns between one and three weeks of age. The condition also affects nearly 30% of adults who live in humid climates.

Symptoms and Causes

What does a heat rash look like?

A heat rash looks like:

A group of small red bumps (1 to 2 millimeters), similar to tiny pimples or blisters.
The skin beneath the bumps is flesh-colored or red to purple.

Where do heat rashes form on my body?

Heat rashes can develop anywhere on your body, but most often appear in creases or folds where skin touches skin. The most common sites of heat rashes include:

Arms and legs.
Neck.
Back.
Underarms.
Groin.
Under your breasts.
Inner thighs.

Heat rashes also form in areas where your clothing rests on your skin for a long period, like the waistband of your pants. Heat rashes rarely form on your face.

What are the symptoms of a heat rash?

Heat rashes form minutes to hours after you start sweating. The heat rash is an area of your skin with clusters of small, pimple-like bumps. Symptoms of a heat rash include:

Prickly feeling.
Mild itch (may be worse with sweating).
Swelling or skin puffs up around rash.
Mild pain or a light burning sensation.

Severe symptoms could occur from a heat rash, especially if you itch it and the bumps break open. Reach out to your healthcare provider if you experience the following severe symptoms:

Rash is warm to the touch.
Pus or clear fluid leaks from bumps.
Severe and persistent itch.
Severe pain.
Fever or nausea.

Are heat rashes itchy?

Yes, heat rashes are usually itchy. Most heat rashes have a mild itch or irritation. More rare cases have severe itching that gets worse the more you itch it. Since the skin where you have a heat rash is sensitive, the bumps on your skin can break open easily when you scratch. This could lead to an infection. If calamine lotion or a prescribed cream doesn’t alleviate your itch, contact your healthcare provider.

Do heat rashes spread?

Yes, heat rashes can spread on your body. Clogged sweat pathways cause heat rashes to spread. A heat rash isn’t bacteria or a virus that can spread to other people, though; heat rashes aren’t contagious. Rashes usually spread in areas where clothing is tight against your skin, especially when you sweat.

What causes a heat rash?

A clog in the narrow pathways (ducts) that carry sweat to the surface of your skin (pores) causes a heat rash. Your body reacts to the clog and attempts to heal it by creating inflammation that forms a rash.

Many factors cause sweat glands to clog, including:

Small pieces of dead skin cells (skin secretions) block your gland.
Too much sweat builds up between your skin and your clothing.
Hair follicles block your glands.
Hormone changes; like being on your period.
Not enough airflow between your skin and clothing.

Heat rashes aren’t caused by being “dirty” or not washing your skin well enough.

Diagnosis and Tests

How is a heat rash diagnosed?

Your healthcare provider will diagnose your heat rash after examining the rash on your skin and asking you questions about your symptoms, especially how long you’ve had symptoms and if any events might trigger the rash, like strenuous physical activity or living in a humid environment.

There aren’t any tests to diagnose a heat rash.

Management and Treatment

How do I treat a heat rash?

Depending on the severity of your heat rash, you can treat your rash at home by:

Keeping your skin cool and dry: Use a fan or air conditioner to cool your body down if the temperature is hot or humid. Take a cool shower and either lightly pat your skin dry with a towel or let your body air dry to prevent further irritation.
Wearing cotton clothing: Choose clothing items made of cotton that allow airflow between the material and your skin. Avoid synthetic materials that often trap heat.
Eliminating friction: Loose-fitting clothing is best to wear around a heat rash to avoid irritation. For heat rashes around your groin area, you could temporarily avoid wearing undergarments to reduce the amount of clothing rubbing against your rash. Babies should also go a few hours without a diaper for heat rashes that affect their diaper region.
Using anti-itch medications: If you have severe itching or pain from your heat rash, your healthcare provider might recommend using a corticosteroid cream or calamine lotion to soothe the area.
Taking medicine to treat any fevers: If your heat rash is induced by fever, try taking an over-the-counter medication, such as Tylenol® or ibuprofen, to bring down your temperature.

How long does it take to get rid of a heat rash?

Once you start cooling your body down, a mild heat rash could go away within a day. On average, heat rashes last two to three days. More severe heat rashes can last up to a couple of weeks without treatment.

If you have a severe heat rash that isn’t going away with at-home treatment and staying cool and dry, contact your healthcare provider.

What shouldn’t I use to treat a heat rash?

Avoid using baby powders, ointments, scented lotions or lotions with petroleum or mineral oils and that could clog your pores and make your heat rash worse.

Prevention

How can I prevent heat rashes?

You can prevent heat rashes by:

Wearing lightweight clothing and clothing that doesn’t cause friction by rubbing on your skin.
Wearing clothing made of cotton and avoiding synthetic fabrics.
Staying in environments with airflow (fans) or an air conditioner if it’s hot.
Keeping your body cool and dry.
Staying hydrated and drinking plenty of water.
Avoiding excessive activity in very hot or humid temperatures.

Outlook / Prognosis

What can I expect if I have a heat rash?

Heat rashes can irritate your skin, which can be itchy or sometimes painful. The rash, on average, will last two or three days. Keeping the affected area of your skin cool and dry is the best treatment. Try not to itch your rash, and use calamine lotion to calm your skin. Make sure you don’t use powders or creams that’ll clog your pores to prevent the rash from becoming more irritated.

If you experience severe symptoms or believe you have an infected heat rash, contact your healthcare provider immediately.

Living With

When should I see my healthcare provider?

If you experience any severe symptoms of a heat rash, contact your healthcare provider. Severe symptoms include:

Pain.
Intense itching.
Rash feels warm to the touch.
Rash becomes infected (leaks pus or fluid, swelling, fever, nausea).
Rash doesn’t go away after at-home treatment or persists for longer than a week.

What questions should I ask my doctor?

Do I need a prescription lotion to treat my heat rash?
Are there any side effects from the treatment you recommend?
Can I continue exercising if I have a heat rash?
What should I do if I get frequent heat rashes?

A note from Cleveland Clinic

While we always enjoy warm summer temperatures, the heat doesn’t always have a positive effect on our bodies. A heat rash might cause mild discomfort and irritation until your body cools down and dries off. Try avoiding wearing tight-fitting clothing and exposing your body to extremely hot or humid temperatures. When in doubt, air it out! Contact your healthcare provider if your rash lasts longer than a week or causes severe symptoms.

What is prickly heat

Prickly heat is also known as sweat rash or miliaria. Prickly heat is a group of skin conditions that arise from blockage of eccrine sweat ducts. Prickly heat is frequently seen in hot, humid or tropical climates, in patients in hospital, and in the neonatal period. There are three types of prickly heat (miliaria) classified by the level of blockage of the sweat duct. These include miliaria crystallina, miliaria rubra and miliaria profunda.

Miliaria (prickly heat) appears in about 15% of newborns. Babies are more commonly affected than children or adults as their sweat ducts are not yet fully developed.

Adults may also be affected, particularly those who work in humid and hot conditions.

Prickly heat rash is uncomfortable but usually harmless. It should clear up on its own after a few days.

The complications of miliaria include:

Secondary bacterial infection, most commonly caused by staphylococci
Impaired thermoregulation
Hyperhidrosis in non-affected areas. In rare cases where a person suffers from chronic and recurrent miliaria rubra or miliaria profunda, a large number of sweat glands may end up not functioning properly. This can lead to compensatory facial sweating.

Miliaria spots can become infected and form abscesses (pus-filled lumps). In addition, when a large surface area of the body is affected, affected individuals can develop a high temperature and suffer from heat stress syndrome.

However, most cases of miliaria resolve within a day or two after changing to a cooler environment without any treatment or complications.

Prickly heat treatment

Miliaria usually disappears after the body is cooled down. It is best prevented by avoiding overheating and over swaddling.

More severe cases (e.g. miliaria profunda) can take several weeks to resolve as time is required for the plugs that block the opening of sweat ducts to be pushed outward by new sweat duct cells.

General measures recommended to improve symptoms:

Avoid further sweating and irritation/friction of the skin.
Good ventilation is important.
Wear loose cotton clothing.
Avoid plastic covered mattresses.

Soothing lotions (e.g. calamine lotion) or topical steroids may help to relieve symptoms.

Antiseptics and antibiotics may be recommended if a secondary infection is suspected.

What are sweat glands?

Sweating prevents overheating of your body, because sweat cools your skin as it evaporates. Only mammals have sweat glands (sudoriferous glands). Humans have more than 2.5 million sweat glands distributed over the entire skin surface, except on the nipples and parts of the external genitalia. Humans normally produce about 500 ml of sweat per day, but this amount can increase to 12 liters (over 3 gallons) on hot days during vigorous exercise. Hair interferes with the evaporation of sweat and the ability to cool the body, so the need for increased temperature regulation through sweating led to a reduction of hairiness in humans.

There are two types of sweat glands, both of which increase their secretion in response to stress as well as to heat: eccrine and apocrine glands.

Eccrine glands (“secreting”) are by far the more numerous type (Figure 1). They are most abundant on the palms, soles, and forehead. Each is a coiled version of a simple tubular gland. The coiled, secretory base lies in the deep dermis and hypodermis, and the duct runs superficially to open at the skin surface through a funnel-shaped pore. (Although most pores on the skin surface are sweat pores, the “pores” seen on the face are openings of hair follicles.)

Apocrine glands are mostly confined to the armpits, anal, and genital areas. They are larger than eccrine glands, and their ducts open into hair follicles. Apocrine glands produce a special kind of sweat consisting of fatty substances and proteins, in addition to the components of true sweat. For this reason, apocrine sweat is viscous and sometimes has a milky or yellow color. This product is odorless when first secreted, but as its organic molecules are decomposed by bacteria on the skin, it takes on a musky smell. This is the source of body odor.

Apocrine glands start to function at puberty under the influence of androgens. Their activity is increased by sexual foreplay, and they enlarge and recede with the phases of a woman’s menstrual cycle. The secretions from the apocrine glands were identified as true human pheromones (chemical signals that convey information to a member of the same species) in the late 1990s when it was shown that they are responsible for the synchrony of the menstrual cycle that occurs in females who live together.

Apocrine glands are involved with sexual signaling and appear to function in attractiveness and mate selection. The genes that encode for the immune system, the major histocompatibility complex (MHC), also influence secretions from apocrine glands. Each person has a unique set of these genes. In experiments, the body odor scents that women selected as “sexy” or “attractive” came from men who had immune system genes most different from their own. Mates with complementary immune system genes provide their offspring with greater disease protection and decreased likelihood of recessive disorders.

Figure 1. Sweat glands

What causes prickly heat?

Miliaria is caused by obstruction of sweat ducts, often from heat and excess sweating.

Miliaria results from sweating. The main contributing causes are:

Immature sweat ducts in a newborn child. A newborn’s sweat ducts aren’t fully developed. They can rupture more easily, trapping perspiration beneath the skin. Heat rash can develop in the first week of life, especially if the infant is being warmed in an incubator, is dressed too warmly or has a fever.
A hot and humid environment.
Intense physical activity. Intense exercise, hard work or any activity that causes you to sweat heavily can lead to heat rash.
Fever
Occlusion of the skin with non-porous dressings or synthetic clothing against the skin
Prolonged bed rest. Heat rash can also occur in people who are confined to bed for long periods, especially if they have a fever.

Common situations in which blockage of the sweat ducts occurs include:

excessive sweating under synthetic clothing
swaddling newborns in multiple garments
lying in bed for long periods (e.g. because of medical illness or immobility), particularly with a fever.

Other diseases and treatments that have been associated with miliaria are:

Adverse reaction to medication (isotretinoin, doxorubicin)
Stevens-Johnson syndrome / toxic epidermal necrolysis
Genetic disease (Morvan syndrome and pseudohypoaldosteronism type I)
Radiotherapy

Prickly heat rash prevention

To help protect yourself or your child from heat rash:

Avoid overdressing. In summer, wear soft, lightweight, cotton clothing. In winter, children should dress only as warmly as an adult.
Avoid tightfitting clothes that can irritate skin.
When it’s hot, stay in the shade or in an air-conditioned building or use a fan to circulate the air.
Keep your sleeping area cool and well-ventilated.

What does prickly heat rash look like?

Miliaria commonly appears in areas of skin that have been blocked particularly around the neck and upper trunk in both children and adults. Other areas that can be affected include the groin, waistline, under the breasts, skin folds and armpits.

Unlike acne, miliaria does not arise around hair follicles.

Miliaria crystallina (miliaria sudamina) appears as small ~ 1–2 mm, superficial and clear blisters. These break easily from mild friction or bathing. There is no inflammation. The blisters are usually seen widely spread on the head, neck, and upper trunk. There is no inflammation. The blisters are usually seen widely spread on the head, neck, and upper trunk. Miliaria crystallina is most commonly seen in neonates with the mean age of 1 week, affecting up to 9% of all neonates (see Figure 2). It can also occur in adults with fever (Figure 3).
Miliaria rubra appears as small, red flat or bumpy spots that are usually very itchy. Miliaria rubra is the most common form of miliaria. It is seen in children and in up to 30% of adults who move to a tropical environment or are unexpectedly exposed to heat and humidity. In children, miliaria affects the skin folds of the neck, axilla or groin. In adults, miliaria often affects the upper trunk, scalp, neck and flexures, particularly areas of friction with clothing. In chronic and recurrent cases, the lesions can turn into pus-filled spots.
Miliaria pustulosa is a variant of milia rubra in which there are pustules.
Miliaria profunda the result of sweat leaking into the middle layer of skin (dermis), appears as deep red or flesh–colored, 1–3 mm diameter papules usually arise on the trunk and extremities. These lesions are generally not itchy as they appear below the itch receptors. Miliaria profunda is rare and presents in adult males. It is a complication of repeated episodes of miliaria rubra.

Figure 2. Miliaria crystallina in an infant – note that the lesions are confluent

Figure 3. Miliaria crystallina

Figure 4. Miliaria rubra

Figure 5. Miliaria pustulosa – is a variant of miliaria rubra in which there are pustules (the pustules are not the result of secondary infection and are self-limiting but can get secondarily infected and can be associated with severe itch)

Prickly heat rash symptoms

The symptoms of prickly heat rash are:

small red spots
an itchy, prickly feeling
redness and mild swelling

The symptoms are often the same in adults and children.

It can appear anywhere on the body and spread, but it’s not infectious to other people.

How is miliaria diagnosed?

Miliaria is most often diagnosed based on the typical appearance of the lesions. The doctor may perform a simple diagnostic test where a fine needle is used to rupture the blister so that the clear fluid/sweat can be assessed.

A biopsy of the skin may be needed to confirm the diagnosis and distinguish it from other conditions that look similar (e.g. erythema toxicum neonatorum, neonatal cephalic pustulosis, candidiasis, Grover’s disease).

The doctor may also request a skin swab to rule out secondary infection.

Individuals who develop heat stress syndrome may need to have blood tests.

Prickly heat rash treatment

Management of prickly heat requires heat and humidity to be controlled to reduce sweating and the avoidance of irritation to the skin. Strategies to avoid sweating and reduce irritation follow.

Work in an air-conditioned office for at least a few hours a day.
Sleep in a ventilated, cool bedroom.
Move away from a tropical climate.
Avoid excessive clothing and tight clothing.
Avoid excessive soap and irritants.
Wear shirts and blouses made of breathable synthetic fabrics or cotton.
Remove wet clothing.

Treatment of miliaria may include:

Cool water compresses
Calamine lotion to relieve discomfort; because of its drying effect, an emollient may be required.
Treatment of fever with antipyretic such as acetoaminophen/paracetamol
Mild topical steroids
Antiseptics and anti-staphylococcal antibiotics for secondary infection.
Avoid using creams and ointments that contain petroleum or mineral oil, which can block pores further.

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