Medical News Today: Prickly heat: Images, causes, and treatment

Miliaria rubra, commonly called prickly heat or heat rash, is a rash that causes a warm, stinging or prickly sensation on the skin. The feeling is usually accompanied by small red dots in the affected area. The rash may also have small blisters.

Prickly heat is often caused by exposure to warm temperatures and will normally clear up on its own after a few days. There are a few simple treatments to help reduce symptoms, but a visit to the doctor may be necessary in some situations.

What is prickly heat?

Prickly heat is the common name for the medical term “miliaria rubia.” It is also known as heat rash. The rash creates an area of red skin with many tiny raised bumps. This area may also blister.

The face, neck, shoulders, and chest are the most common places for prickly heat to occur, although it may show up anywhere. While it can affect anyone, children are more likely to get prickly heat than adults.


prickly heat (Miliaria rubra)
Prickly heat commonly occurs in the neck, chest, shoulders, and face.

Prickly heat is usually easy to identify due to its straightforward symptoms. Tiny red bumps and itching on an area of skin that has been exposed to heat and sweat for a long time are common signs of prickly heat.

Sometimes the red bumps can develop into a series of tiny blisters. The bumps or blisters may swell, become irritated or itchy, and redden as the rash progresses.

Prickly heat may spread on the body, but it is not infectious. Under normal conditions, there is no way to pass the rash on to other people.

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Causes and triggers

Prickly heat is caused by trapped sweat. When the body is hot, it activates the sweat glands to create sweat on the skin. The sweat then cools the skin as it evaporates.

When the body is kept in this warm state, the constant sweat production can overload the sweat glands. This can cause the sweat ducts to become clogged, trapping sweat in the deep layers of the skin. This trapped sweat irritates the skin, which responds by producing a rash.

The most common trigger for prickly heat is exposure to heat for a long time. This may be especially true in very humid areas where the sweat has a harder time evaporating off the skin.

Prickly heat is common in people from cooler climates who travel to warmer climates. But it may also happen to a person in their usual climate when they experience more heat and sweat than normal.

Certain medications can also trigger prickly heat. Any drugs that raise the body temperature or alter the function of the sweat glands can increase the risk of prickly heat.

Some medications for Parkinson’s disease block the sweat, and tranquilizers and diuretics can change the fluid balance in the body, which can trigger symptoms of prickly heat as well.

A study in JAMA Dermatology noted that prickly heat developed where the bacteria Staphylococcus were found. These bacteria are normal, but the biofilm they produce can block sweat ducts and contribute to skin conditions. This would suggest that people with Staphylococcus on their skin may be more prone to prickly heat than others.


cold shower
Cooling off to avoid additional sweat is recommended to treat prickly heat.

Prickly heat will usually go away on its own, but it may have bothersome symptoms. Many people can benefit from using home remedies. Calamine lotion or topical steroid creams can help treat the symptoms of redness, irritation, and swelling.

Treating prickly heat also involves cooling off quickly to avoid additional sweat. Sitting in front of a fan or in an air-conditioned room can help. Cold showers or baths can reduce body temperature and help prickly heat clear up faster.

Camphor and menthol may also have a cooling effect on the skin and help reduce the itchiness. In some cases, antihistamine medications can help reduce itching.

People who are prone to prickly heat may find relief from regularly washing the body with mild soap after sweating. This can reduce the amount of sweat and the number of bacteria on the skin.

Prickly heat in children and babies

Prickly heat can occur in people of all ages, is more common in children and infants. The developing sweat glands in a small child are less resilient and may be more likely to become clogged. Also, a child’s body is not used to adjusting to rapidly changing temperatures.

Children and infants are likely to experience prickly heat on their groin, neck, and face. The rash may be irritating and uncomfortable, but it will usually go away on its own. A cool bath can provide a child or baby with some relief from symptoms.

Parents and caregivers should avoid using oil-based skin products on children and infants to reduce the risk of clogging their sweat glands.

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heat rash <br>Image credit: Sentient Planet, 2011</br>
Skin products may clog the pores and lead to prickly heat.
Image credit: Sentient Planet, 2011

Preventing sweat from becoming trapped in the skin is an important step to avoid a rash. This may be as simple as not using certain skin products. Skin products that contain heavy oils or petroleum jelly may clog the pores and sweat glands, which could contribute to prickly heat.

Loose fitting clothing made of natural fibers, such as linen, cotton, and hemp, may reduce the amount of sweat that gets trapped on the skin.

Removing sweaty clothes after a long day of warm weather can prevent the sweat from getting trapped in the skin. Taking a shower to wash off the sweat and changing into clean clothes can prevent many cases of heat rash.

Avoiding a long time in hot and humid environments may help prevent symptoms, as well as using fans and air conditioners when possible. Regular cool showers or baths can reduce the body’s temperature and prevent excessive sweating.

When to see a doctor

Prickly heat is a common condition that will usually resolve without medical treatment. Taking steps to prevent heat rash is the best way to avoid this annoyance.

If prickly heat starts to show, it may help to take a few quick steps to lower the body’s temperature and prevent additional sweating. Watching for any additional signs of heat stroke or exhaustion can help prevent a more serious issue.

If the symptoms of prickly heat persist or the rash seems to become infected, a person should seek medical attention. They may be referred to a dermatologist if there are signs of an underlying condition.

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