Types of Heat Rash

There are three main types of heat rash (miliaria), depending on how deep in the skin the blocked sweat duct is.

Miliaria crystallina

The mildest and most superficial type. Clear, tiny, fluid-filled blisters that look like drops of water appear on the surface. They usually do not itch or hurt and break easily. It is common in newborns and after fever.

Miliaria rubra (prickly heat)

The most common type in hot, humid places. The duct is blocked deeper in the outer skin. It causes red bumps, with itching and a prickling or stinging feeling. The area can be sore. If untreated and skin gets infected, small pus-filled spots can appear, called miliaria pustulosa.

Miliaria profunda

A less common type that affects the deeper layer of skin. It causes firm, flesh-coloured bumps that look like goose bumps. It tends to follow repeated bouts of miliaria rubra, and sweating is reduced in the affected area, which can make the body overheat. It mainly occurs in adults in hot climates and needs medical care.

Related conditions that can look similar

• Folliculitis, infection of hair follicles
• Contact dermatitis or eczema, with different triggers and itching patterns
• Fungal infection and candidal rash in skin folds
• Insect bites and chickenpox, which can look like blisters

Ayurvedic view

Ayurveda describes heat-related skin eruptions linked to pitta. This is a traditional framework, not a classification used by doctors.

Key point

Most heat rash is crystallina or rubra and resolves with cooling. Deeper or repeated rashes need a doctor.

Before your appointment

Note when the rash began, where it is and what makes it better or worse, such as heat, clothes, creams or sweating. List any products, medicines, oils or herbal pastes you have used, and whether anyone at home has a similar rash. For a baby, note fever, feeding, and what the baby wears and sleeps in. Take photos of the rash over a few days.