Signs and Symptoms of Heat Rash

Heat rash—also sometimes called prickly heat or miliaria—is a skin condition that causes patches or clusters of small, red bumps that often feel intensely itchy or cause stinging sensations. The condition commonly develops in hot, humid weather when your sweat glands become blocked and trap sweat under the skin. Anyone can develop heat rash, but babies and young children experience symptoms at a higher rate because their sweat glands are underdeveloped.

Most people experience heat rash within minutes to hours after sweating or spending time in the heat. It's common to notice heat rash symptoms on your neck, back, chest, thighs, and groin area. While heat rash can be uncomfortable, it is not contagious and usually resolves within three days. That said, knowing the different types of heat rash and the symptoms of each can help you understand how to treat your condition and when to reach out for medical care if needed.

Common Symptoms 

There are four common types of heat rash, and the exact type you have will depend on which layer of your skin sweat became trapped in. While each type has its own set of unique symptoms, there are some common characteristics that all the types share. These symptoms include:

• Clusters of tiny bumps on the skin
• Itchiness 
• Redness and swelling 
• Prickling (a feeling of “pins and needles”), burning, or stinging sensations around the skin
  

Heat rash usually develops on parts of the skin with the highest concentration of sweat glands, such as the chest, back, armpits, neck, groin, and other skin folds where clothing can easily rub against your skin.

Miliaria Crystallina Symptoms 

Miliaria crystallina is the mildest form of heat rash that develops when sweat becomes trapped in the top layer of the skin. This type of heat rash is most common among newborns and adults who recently moved or traveled to hot and humid areas. Symptoms of miliaria crystallina include:

• Tiny and clear, fluid-filled blisters on the surface of the skin 
• Blisters that easily rupture, usually without pain 
  

Unlike other types of heat rash, miliaria crystallina is generally painless and does not cause intense itching or discomfort. 

Miliaria Rubra Symptoms 

Miliaria rubra, or “prickly heat,” is the most common form of heat rash. You might experience this rash when sweat becomes trapped deeper in the outer layers of your skin. This type is most common in infants and adults who live in humid climates.

Symptoms of miliaria rubra typically occur due to prolonged exposure to heat and humidity and may include:

• Small, red bumps on the skin
• Intense itching or prickling sensation in the affected area
• Redness, discomfort, and inflammation around the bumps
• Lack of sweat near the rash
• Worsening symptoms when exposed to sunlight or humidity

Miliaria Pustulosa Symptoms 

Miliaria pustulosa occurs when miliaria rubra progresses, causing pus to form in the bumps. If you develop this type of heat rash, you might experience:

• Small, yellowish, or white pustules (bumps) on the skin
• Red, inflamed skin around the bumps 
• Itchiness or tenderness in the affected area 
  

If you're experiencing this heat rash type, it's important to refrain from scratching the bumps. Scratching your skin can cause the bumps to burst open and increase your risk of developing a bacterial infection. 

Miliaria Profunda Symptoms 

Miliaria profunda is the rarest but most severe form of heat rash. This condition occurs when sweat is trapped deep beneath the skin. Oftentimes, this rash can develop in people who experience recurrent (repeat episodes) miliaria rubra. Generally, symptoms appear on the chest, arms, and upper back and may include the following:

• Large, raised, flesh-colored bumps 
• Pain and discomfort in the affected area
• A rough, sandpaper-like feeling on the skin due to blocked sweat ducts 
• Fatigue due to a decreased ability to sweat

Symptoms in Infants and Children 

Heat rash is common in infants and young children, especially during the summer and in hot and humid climates. Underdeveloped sweat ducts make infants and young children more prone to heat rash, which can often cause symptoms in parts of the body such as their necks, faces, chest, arms, legs, and diaper areas.

If you suspect your child has symptoms of heat rash, check for the following signs:

• Small, flesh-colored bumps on the skin
• Skin that is warm or tender to the touch
• Tiny fluid-filled blisters
• Increased irritability or fussiness due to itchiness or discomfort 

When to Contact a Healthcare Provider 

Most cases of heat rash resolve without treatment within three days. But, it's good practice to contact a healthcare provider if:

• Symptoms worsen or do not go away after three days 
• There are signs of infection, such as pus, oozing, or fever 
  

It's worth noting that there are some instances of heat rash where you should seek urgent medical attention. If you or your child have a heat rash and experience any of the following heat-related illness symptoms, contact your healthcare provider as soon as you can:

• Fever
• Dizziness
• Nausea
• Rapid heart rate 
• Difficulty breathing 

A Quick Review 

Heat rash is a common, but uncomfortable skin condition that often develops in hot and humid weather. Different types of heat rash can cause various symptoms, ranging from clear, fluid-filled blisters to red, inflamed, intensely itchy bumps. Anyone can develop a heat rash, but infants and children tend to be more susceptible to the condition.

Staying cool and wearing loose-fitting, lightweight clothing can help manage heat rash symptoms. Talk to a healthcare provider if heat rash symptoms last longer than three days, worsen, or you or your child show signs of heat-related illness.