The Medical Dermatology Program at Massachusetts General Hospital is a full-service dermatology practice that provides care for all skin, hair and nail conditions.
What is prickly heat?
Prickly heat is a skin rash caused by sweat trapped in the skin. Normally, sweat travels to the surface of the skin through tiny ducts. If the ducts become narrowed or clogged, the sweat is trapped in the skin. This can cause redness, itching, and small blisters. The rash often appears on the torso and thighs, especially where skin touches skin. Prickly heat tends to be more common in hot, humid climates.
What causes prickly heat?
The condition is caused by narrowed or clogged sweat ducts. This may be because of things that cause sweating, such as:
Hot, humid weather
A lot of physical activity
Illness with fever
Tight or warm clothing
Medicine patches that stick to the skin
Health conditions that cause extra sweating (hyperhidrosis)
It may also be from:
Some medicines, such as isotretinoin or beta blockers
Who is at risk for prickly heat?
You are more at risk for prickly heat if you sweat a lot, but it is more common in children.
What are the symptoms of prickly heat?
Symptoms can occur a bit differently in each person. They can include:
Irritation that feels like prickling
Small bumps or blisters
Large, red areas of skin
The symptoms of prickly heat can be like other health conditions. Make sure to see your healthcare provider for a diagnosis.
How is prickly heat diagnosed?
Your healthcare provider will ask about your symptoms and health history. They will give you a physical exam. The physical exam will include looking closely at your skin.
If you have severe symptoms, your healthcare provider may do a skin biopsy. They will remove a small piece of skin to send to a lab.
How is prickly heat treated?
Treatment will depend on your symptoms, your age, and your general health. It will also depend on how severe the condition is.
The rash usually goes away on its own when sweating is prevented. You can do this by:
Keeping your skin cool and dry
Wearing lightweight, loose clothing
Wearing fabric that lets air get to the skin, such as cotton
Removing bandages or patches
Other treatment may include:
Using a gentle exfoliator in the bath or shower
Corticosteroid cream or lotion to help reduce itching and inflammation
Antibiotic cream or lotion if bacteria is part of the cause
Talk with your healthcare providers about the risks, benefits, and possible side effects of all medicines.
What are possible complications of prickly heat?
In rare cases, blocked ducts may cause damage to sweat glands. This is called miliaria profunda. The sweat glands stop working (anhidrosis). This causes problems with the body cooling itself normally with sweat. You can then be more easily overheated (hyperthermia).
Can prickly heat be prevented?
You can help prevent the problem by:
Staying in cool environments
Wearing lightweight, loose clothing
Taking other steps to prevent extra sweating
When should I call my healthcare provider?
Call the healthcare provider if you have:
Symptoms that don’t get better, or get worse even after using suggested treatments
Key points about prickly heat
Prickly heat is a skin rash caused by sweat trapped in the skin. It tends to be more common in hot, humid climates.
Symptoms include redness, itching, and small blisters.
The condition is caused by narrowed or clogged sweat ducts. This may be from things that cause sweating, such as hot, humid weather or physical activity.
The rash usually goes away on its own when sweating is prevented. You can do this by keeping your skin cool and dry.
Treatment may also include corticosteroid cream or lotion to help reduce itching and inflammation.
Tips to help you get the most from a visit to your healthcare provider:
Know the reason for your visit and what you want to happen.
Before your visit, write down questions you want answered.
Bring someone with you to help you ask questions and remember what your provider tells you.
At the visit, write down the name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are.
Ask if your condition can be treated in other ways.
Know why a test or procedure is recommended and what the results could mean.
Know what to expect if you do not take the medicine or have the test or procedure.
If you have a follow-up appointment, write down the date, time, and purpose for that visit.
Know how you can contact your provider if you have questions.
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