Heat rash


A heat rash occurs when sweat is trapped in the pores and ducts beneath the skin, leading to skin irritation. This type of rash typically emerges in regions with inadequate airflow or where skin-to-skin contact is prevalent. It can impact individuals of any age, with babies, infants, and toddlers being particularly vulnerable due to the ongoing development of their glands and ducts.

Heat rashes are a common occurrence in conditions characterized by high temperatures and humidity. The sweat cannot efficiently leave the body which results to tiny pimples, or blisters to form, causing discomfort. Heat rash is also known as prickly heat rash, sweat rash, or miliaria.

The rash may cause discomfort or itching. Manage the rash at home by maintaining cool and dry skin. If the rash persists for more than a week or results in intense pain or discomfort, medical intervention may be necessary.

Types of heat rash

Heat rashes are categorized based on the depth at which sweat is trapped within the skin, with varying signs and symptoms for each type:

  • Miliaria crystallina: This occurs when the sweat duct openings at the skin’s surface are obstructed, resulting in tiny, easily breakable, transparent, fluid-filled bumps. This is the mildest form of heat rash.
  • Miliaria rubra (prickly heat): Usually accompanied by itching or prickling sensations in the affected region, this variant occurs deeper within the skin, manifesting as small, inflamed blister-like bumps.
  • Miliaria pustulosa: This particular form occurs when the inflamed bumps of miliaria rubra accumulate in pus.
  • Miliaria profunda: A less prevalent type of heat rash affects the deepest skin layer, known as the dermis. This variant causes firm, painful, or itchy inflamed bumps that resemble goosebumps and may rupture.


Heat rashes typically emerge within minutes to hours of sweating, presenting as clusters of small, pimple-like bumps on the skin. In adults, these rashes commonly appear in skin folds and areas where clothing causes friction. Infants often experience a rash on their neck, shoulders, and chest, with additional occurrences in the armpits, elbow creases, and groin.

Common symptoms may also include:

  • Prickly sensation
  • Slight itching, potentially exacerbated by perspiration
  • Inflammation or skin swelling occurs around the rash
  • Mild discomfort or a gentle burning feeling

If the rash persists despite at-home treatments or extends beyond a week, consult a healthcare provider for proper diagnosis and treatment. Cooling the skin and removing the causing heat source are the usual methods that heat rash is treated.

In cases of severe heat rash with symptoms such as pain, intense itching, a warm sensation in the affected area, signs of infection such as pus or fluid leakage, swelling, fever, and nausea, urgent medical attention is necessary.


A heat rash occurs when the passage or duct connecting a sweat gland to the skin’s surface is obstructed or inflamed. Due to the obstruction, the body initiates inflammation to heal it, leading to the formation of a rash.

Various factors contribute to the blockage of sweat glands, such as:

  • Excessive sweat pooling between the skin and clothing
  • Inadequate airflow between the skin and clothing
  • Accumulation of small fragments of dead skin cells (skin secretions) obstructing the glands
  • Hair follicles impeding the glands
  • Hormonal fluctuations, such as during menstruation

It should be noted that heat rashes are not caused by being “unclean” or insufficiently washing the skin.

Risk factors

Heat rashes can impact individuals of all ages. However, several factors may contribute to one’s risk of having one, such as:

  • Being a newborn, infant, or toddler, due to their developing glands and ducts. They are also bundled up or dressed in multiple layers, increasing susceptibility.
  • Residing in a hot and humid environment
  • Being an athlete, or engaging in physical activity
  • Prolonged bed rest coupled with a fever as clothing remains in contact with the skin and another surface for prolonged periods.