Heat rash

Astrid Leitner studied veterinary medicine in Vienna. After ten years in veterinary practice and the birth of her daughter, she switched - more by chance - to medical journalism. It quickly became clear that her interest in medical topics and her love of writing were the perfect combination for her. Astrid Leitner lives with daughter, dog and cat in Vienna and Upper Austria.

More about the experts All content is checked by medical journalists.

Heat rashes (miliaria) occur when the sweat glands are blocked and the sweat cannot evaporate from the skin. Small, translucent, milky, or red blisters form that are usually harmless and will heal on their own. Read here how you can recognize a heat rash, what works against it and how you can prevent it!

ICD codes for this disease: ICD codes are internationally recognized codes for medical diagnoses. They can be found, for example, in doctor's letters or on certificates of incapacity for work. L74

Brief overview

• Symptoms: Millet grain to pinhead-sized, transparent, milky or reddish skin vesicles, which occur mainly on covered parts of the body (torso, chest, groin, back, diaper area)
• Treatment: The rash usually heals on its own after a short time. If necessary, itch-relieving and anti-inflammatory ointments, creams or tinctures. Antibiotic or antifungal ointments for bacterial or fungal infections.
• Causes: Clogged sweat glands due to excessive sweat production, the sweat can no longer evaporate on the skin and collects under the surface of the skin.
• Risk factors: Extreme heat, tight-fitting or too warm clothing, high humidity (humid heat, tropical regions), physical exertion
• What are heat rash? Heat rash is a harmless skin disease, doctors also call it miliaria.
• Diagnostics: Typical appearance of the vesicles
• Prevention: Avoid direct sun, wear loose, breathable clothing (cotton, silk), keep skin cool and dry, no physical exertion in extreme heat and high humidity

What do heat rashes look like?

What the pimples look like in a heat rash depends on where in the duct the welding nozzle is clogged.

Symptoms of miliaria cristallina / alba

With this form of sweat blister, the sweat gland is closed on the surface of the skin (horny layer).

• Millet grain to pinhead-sized, bright, plump blisters (resemble drops of sweat)
• Blisters are filled with clear (Miliaria cristallina) or milky liquid (Miliaria alba).
• The wall of the vesicles is very thin, they burst spontaneously or when wiped away with the hand.
• No inflammatory changes
• Usually no itching

Symptoms of miliaria rubra / profunda

In this type of rash, the sweat glands in deeper layers of the skin are blocked. The sweat does not reach the surface of the skin, but collects in the gland until it bursts. The sweat passes into the surrounding tissue and causes inflammation there.

• The smallest, intensely red, point-like spots or papules develop.
• In the further course, small vesicles form on it.
• Closely spaced vesicles flow together and form oozing, red spots.
• If skin bacteria penetrate the damaged skin, small, yellowish pus pustules form.
• Itching or burning

Typical spots for heat rash

The rash forms wherever there are many sweat glands. Typical places on the body are:

• On the cleavage
• Under the armpits
• On the thighs
• Between the shoulder blades
• In the back of the knees
• In skin folds where moisture and heat accumulate: groin, diaper area, under the breasts

What can you do about heat rash?

In most cases, the sweat blisters (sweat frizzles) heal on their own. Treatment is only necessary if the skin becomes inflamed, itchy, or if there is an additional bacterial or fungal infection.

What can i do on my own?

• Look for a place in the shade!
• Take a lukewarm shower; the water frees the skin from sweat and cools it.
• Keep your skin dry!
• Put on loose-fitting clothes made of cotton or linen.
• Avoid alcohol, coffee, hot spices and lavish food; they increase sweating.
• Drink enough, preferably water or sage tea. The essential oils of sage inhibit sweat production.
• Put cold compresses or a damp washcloth on the affected areas (no ice directly on the skin).
• Do not scratch heat pimples, otherwise large-scale inflammations can occur!

Medication

• Zinc oxide shaking mixture: dries out the skin, has an itch-soothing and anti-inflammatory effect
• Ointments containing cortisone reduce inflammation and soothe itching.
• In some cases, the doctor will prescribe antihistamines for itching.
• Antibiotic ointments help with bacterial inflammation of the skin.
• In the event of a fungal attack, the doctor will prescribe an antifungal ointment.

What are the causes of heat rash?

The cause of heat rash is blocked sweat glands. Normally, the sweat from the sweat gland is conducted through an outlet duct to the surface of the skin in order to evaporate there. Heat pimples occur when this duct is blocked. This is the case when the body produces a lot of sweat but cannot evaporate enough sweat from the surface of the skin. The sweat collects in the gland and forms a blister.

The reasons for this are:

• Big heat
• Profuse sweating during physical exertion or febrile infections
• Tight-fitting or warm clothing (especially for babies and toddlers)
• Non-breathable clothing (synthetic fabrics such as polyester)
• High humidity (humid heat, tropical regions)

description

A heat rash is a mostly harmless skin disease (dermatitis hidrotica) that occurs when the outlets of the sweat glands are blocked. Doctors also refer to the so-called heat rash as miliaria. The term is derived from the Latin word "milium". It means "millet" and describes the appearance of the pimples: light to reddish blisters that are about the size of millet or pinhead and are filled with liquid.

Everyone has up to four million sweat glands. When exposed to high temperatures or physical exertion, they exude sweat. This evaporates on the skin and thus cools the body. The evaporation process protects the organism from overheating.

Forms of heat rash

Depending on where the sweat glands are blocked, doctors differentiate between different forms of heat rash.

Miliaria cristallina (Dermatitis hidrotica, Hidroa, Sudamina, sweat frizzles, heat flakes): In this form of heat rash, the sweat gland on the surface of the skin (horny layer) is blocked. The cause is profuse sweating in febrile infections or clothes that are too warm, especially in babies and toddlers. The vesicles are up to the size of a pinhead and filled with clear or milky (Miliaria alba) liquid. The skin is otherwise unchanged, and those affected do not feel itchy. When the skin is cooled and cleaned, the rash will go away on its own within a few hours.

Miliaria profunda: With these heat pimples, the duct of the sweat gland is blocked in the deeper layers of the skin. The sweat penetrates the surrounding tissue and causes inflammation there. The vesicles appear intensely red (Miliaria rubra, Red Dog) and itch.

Who is affected?

Heat rash can occur in people of all ages. Infants and children are particularly often affected. The reason for this is, on the one hand, that their skin is thinner and more sensitive compared to adults. In addition, their sweat glands are not fully developed and tend to become clogged. On the other hand, they are often too warmly dressed. This causes the heat to build up under warm clothing and clog the sweat glands.

In adults, the skin vesicles form mainly in situations in which the sweat cannot evaporate from the skin. This is the case with high humidity (humid heat), tight-fitting or non-breathable clothing.

The heat rash develops particularly often when traveling to tropical regions. The high humidity prevents sweat from evaporating, especially in people who are not acclimatized. Typically, the vesicles appear within a few days.

Investigation and diagnosis

A doctor's visit is necessary if the skin becomes inflamed or the itching is severe. Possible contacts in the event of heat rash are the pediatrician, family doctor or dermatologist. The doctor makes the diagnosis based on the typical skin changes and the patient's history.

Course of the disease and prognosis

A heat rash is usually harmless and the blisters usually heal completely within a day or two.

In Miliaria cristallina and alba, the vesicles are so superficial that they either burst by themselves or when touched lightly. If the skin is no longer exposed to the heat, freed from sweat and dried, the blisters will disappear within a few hours, even without treatment.

With reddish heat pimples (Miliaria rubra / profunda) the skin is inflamed. At these points, skin bacteria have the chance to penetrate the skin and trigger additional bacterial inflammation. Doctors speak of a secondary infection.

Fungal spores feel good in skin folds where it is damp and warm, such as in the groin or under the breasts. A fungal attack on the skin manifests itself as weeping, blotchy reddening.

Can you prevent heat pimples?

Tips to prevent sweat blisters:

• Wear loose, breathable clothing made of cotton or silk when it is very hot and humid.
• Avoid the direct sun.
• Use sunscreen without fragrances or preservatives so as not to irritate the skin additionally.
• Refrain from physical exertion (sport, heavy physical work) when it is very hot.
• Keep your skin cool and dry.
• Take a shower with lukewarm water to wash the sweat off your skin. It is best to avoid shower gel, as it irritates the skin even more.
• After showering, apply a light body lotion to your skin.
• A cotton sheet is enough to cover the night at high temperatures.
• Regular, gentle body scrubs help rid the skin of dead skin.

Tips for traveling to tropical regions:

When traveling to tropical areas, it is important to slowly get your skin used to the high humidity. Avoid the blazing sun, especially in the first few days, and refrain from physical exertion. Loose and breathable clothing, for example made of cotton, allows sweat to evaporate better on the skin.

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