Miliaria - Causes and Treatment

The miliaria, popularly known as prickly heat, is a skin eruption characterized by the appearance of small bubbles, which can be light or reddish. The rash is a common dermatitis, particularly in children and infants, and is caused by obstruction of the ducts of the glands that produce sweat.

In this article we will explain what is the prickly heat, what its causes are, their risk factors, symptoms and what are the best treatments.



We are able to sweat because we have glands that produce sweat, called sweat glands and ducts that carry this sweat glands of the skin. The rash is a skin eruption caused by obstruction of these ducts, also known as pores of the skin, preventing the sweat produced reach the outermost layer of the skin. With the clogged ducts, the sweat produced is trapped in the innermost layers of the skin, causing rupture of the duct and an inflammatory reaction, which are the clinical translation of prickly heat rash.

The rash can occur at any age but are more common in babies and young children, because they have smaller pores, and their glands and ducts are still very immature. In general, rash on the baby usually arise from the first week of life.

As there are virtually sweat glands throughout the body, any skin site is subject to develop a rash. The rash, however, occur more frequently in areas of the body to sweat more, which are usually folds and parts covered by clothing. Trunk, neck, belly, below the breasts, buttocks, armpits and groin are especially susceptible areas. In babies, the face is a common area as well.

The area covered by the diaper can also develop miliaria, however, it is important not to confuse the rash with diaper rash, which is the famous roast.

We do not know fully even the pathophysiological mechanism that leads to blockage of the sweat ducts, however, some important risk factors have been identified:

• Immature ducts: Because the ducts of babies are not fully developed, they are more fragile and can break easily, holding the sweat under the skin. This problem usually happens in times of heat, but can occur at any time if the children are very thick and warm clothes.
• Fever: Newborns and infants who are with high fever may also develop rashes because your body is perspiring excessively. The fever can also cause heat rash in adults, especially those who are bedridden, with the back constantly in contact with the bed.
• Summer: the warmer the environment, the more children sweats, and the greater the risk of rashes appear.
• Intense physical activity: in adults, a frequent cause of rash is physical activity, especially if it gets too hot.
• Clothing type: Some fabrics are not suitable for hot days or to perform physical activities because they prevent the evaporation of sweat, making it difficult to reduce body temperature and further stimulates sweat.
• Creams and powders: some products applied to the skin can block the pores, favoring the onset of rash.

The appearance of a rash may vary according to the depth of the obstruction of the sweat ducts. In general, we have three types of miliaria:

Miliaria crystalline

The crystalline miliaria is the mildest form of heat rash. It arises when the duct obstruction is very superficial. The crystalline miliaria presents itself as vesicles (tiny bubbles), grouped and with clear liquid inside with no signs of inflammation around them. This type of rash usually does not cause symptoms, and there is no pain or itching.

Miliaria rubra

The miliaria rubra is the most common form of heat rash. When the obstruction of the ducts is somewhat deeper, sweat leakage into the lower layers of the skin often cause local inflammation, reflected clinically as small reddish skin bubbles, which tend to itch. Pain or burning sensation are also common.

As the ducts are blocked, there is no sweat in the affected area, which can leave the skin more dry.

When the patient presents with repeated episodes of Miliaria rubra, you can develop deep miliaria , a form of heat rash which presents with skin-colored nodules appearing immediately after the start of physical activities or contact heat. This form of heat rash can affect large areas of skin, preventing the individual sue properly to cool your body and may cause shock excess heat.

Miliaria pustular

The pustular miliaria is a more unusual form of heat rash. When the obstruction of the ducts is deep, very close to the sweat glands, the skin lesions become larger, with signs of inflammation and pus inside the vesicles.

The prevention of prickly heat is not always possible, especially in infants living in hot climates. However, you can reduce the intensity and frequency avoiding very warm clothes, tight or tissues that hinder evaporation sweat. Made of cotton clothes are the best.

In hot weather, avoid bathing with very hot water and let the child in cooler places, either with fans or air conditioning if possible. If the baby is developing rashes often or it is being exposed to too much heat or your clothing is not appropriate.

In cases of adults who perform physical activities, it is important to wear appropriate clothing for those who will sweat intensely. Bath with cold water helps to prevent prickly heat, especially in hot weather.

The crystalline miliaria is an asymptomatic dermatitis, harmless and spontaneous resolution of 3 or 4 days. Therefore, this form of heat rash does not require any treatment. It serves as a warning only for you or your baby using appropriate clothing and are less exposed to heat.

The miliaria rubra is also a benign lesion, but can be quite uncomfortable. If there is a lot of itching or burning, in addition to preventive measures mentioned above, the patient can use calamine lotions, menthol or anhydrous lanolin.

Rash in babies, it is best not to use any medication without consulting with a pediatrician. Skin lesions are extremely common in infants and several of them can resemble a rash. Avoid using creams and lotions on their own, as well as talc, as these substances can cause even more clogged pores, exacerbating the symptoms.

In most cases, the heat rash requires no treatment in addition to the care with moisture and heat.