Conditions
Heat rash: relief and when to see a doctor
Heat rash (prickly heat, or miliaria) is a patch of small red bumps or tiny blisters that appears when sweat gets trapped in the skin, especially in Puerto Rico's heat and humidity. It usually clears once the skin cools down and you wear loose cotton clothes. If it does not improve, itches a lot or worries you, the doctor can check it by video, for adults and children of all ages.
Is it an emergency? Call 911.
Is this an emergency?
This is not an emergency service. Call 911 or go to the nearest emergency room if you have:
- Confusion, fainting or very hot skin after being in the heat
- A baby under 3 months with a temperature of 100.4 °F (38 °C) or higher
- A rash with fever and spots that do not fade when you press on them
- Redness that spreads fast, with fever or severe pain
Help lines
At a glance
Heat rash
Common symptoms
- Small red bumps or tiny blisters
- Itching or a prickling feeling
- Appears where you sweat or skin folds: neck, chest, groin, armpits
- Other names
- Prickly heat · Miliaria · Sweat rash
- Treatment
- Cooling and drying the skin, loose cotton clothing; no heavy creams
On this page(9)
What is heat rash?
Heat rash, also called prickly heat or miliaria, is skin irritation caused by heavy sweating in hot, humid weather. It happens when the pores of the sweat glands get blocked and sweat cannot get out.
It is common in adults who work or exercise in the sun, in visitors who are not used to the island's heat and, very often, in babies who are dressed too warmly. It is not contagious.
How we help by video
You see Dr. Diana Nieves Castro, a Puerto Rico–licensed general practice physician with several years of emergency-department experience, in English or Spanish. The doctor asks when it started, where it is and what you have tried, and looks at the rash on camera. If she asks, you can send photos through the secure link.
We evaluate, diagnose and treat. The doctor confirms whether it is heat rash or something that looks similar, such as a fungal rash, eczema or a skin infection. If appropriate, the doctor prescribes and we send your prescription to your pharmacy. Visiting the island? We see you too: see care for visitors.
Your doctor
Dr. Diana Nieves Castro, MD
General practice physician
Several years of emergency-department experience.
Founding Executive Director of The Health Initiative.
Your visit in 3 steps
Request a visit online 24/7 — we confirm your time by email or text.
Request your visit.
Book a visit and choose "Doctor visit". You pay by card when you request it.
See the doctor by video.
We send you a secure video link. It works on your phone, tablet or computer.
Get your plan.
The doctor explains how to care for your skin and, if appropriate, prescribes and we send your prescription to your pharmacy.
What the visit costs
Heat rash is handled in a US$79 doctor visit, the same price for every age, with no membership. You pay by card when you request the visit, and you get a full refund if the visit can't take place. We do not bill insurance. The service is run by The Health Initiative, a nonprofit.
Heat rash symptoms
According to the CDC, heat rash looks like red clusters of pimples or small blisters. It usually appears on the neck, upper chest, groin, under the breasts and in elbow creases. In babies and children it also shows up in the armpits, on the thighs and where clothes rub.
- Small red bumps or tiny blisters
- Itching or a prickling feeling
- Appears where you sweat or skin folds: neck, chest, groin, armpits
How to relieve heat rash
Cooling and drying the skin is what helps most:
- Move somewhere cooler and less humid: shade, air conditioning or a fan.
- Rinse sweaty areas with cool water and pat dry.
- Wear loose, lightweight cotton clothes.
- Skip heavy creams and ointments: they keep the skin warm and block the pores.
Heat rash in babies
Babies often get heat rash when they are bundled up. Dress your baby in light, soft cotton clothes, and if there is no air conditioning, use a fan set to a gentle breeze. MedlinePlus advises against powders, creams and ointments: powders do not help, and creams block the pores.
If your baby has a fever, seems ill or is very sleepy, it is not just heat rash: have your baby seen in person. See rash in children. Patients under 21 need a parent or legal guardian on camera with ID during the visit.
For safety: a baby under 3 months with a temperature of 100.4 °F (38 °C) or higher needs the emergency room right away.
When to go to the ER
Heat rash itself is not dangerous, but heat can be. Know the signs of heat exhaustion and heat stroke. For your safety, go to the ER or call 911 if you notice:
- Confusion, fainting or very hot skin after being in the heat
- A baby under 3 months with a temperature of 100.4 °F (38 °C) or higher
- A rash with fever and spots that do not fade when you press on them
- Redness that spreads fast, with fever or severe pain
How we care for you
We evaluate, diagnose and treat; if needed, we give you a lab order for a lab near you.
We see adults and children of all ages. Patients under 21: a parent with patria potestad (parental authority) or a legal guardian is on camera for the whole visit and shows photo ID.
Real-time video visit. We send you a secure video link. It works on your phone, tablet or computer.
If appropriate, the doctor prescribes and we send your prescription to your pharmacy. We do not prescribe controlled substances.
You must be physically in Puerto Rico during the visit (visitors, tourists and cruise passengers are welcome).
In an emergency, call 911.
Frequently asked questions
How long does heat rash last?
Should I put powder or cream on my baby's heat rash?
Is heat rash contagious?
Can I be seen while on vacation in Puerto Rico?
About this page
Author: The Health Initiative
Medical care provided by Dr. Diana Nieves Castro, MD (PR license 24027)
Disclosure: Founding Executive Director of The Health Initiative
Published: 2026-10-02 · Updated: 2026-10-02
Sources (3)
- Heat-related illnesses: heat rash (CDC/NIOSH) (opens in a new tab) (accessed 2026-10-02)
- Babies and heat rashes (MedlinePlus, NIH) (opens in a new tab) (accessed 2026-10-02)
- 12 Common Summertime Skin Rashes in Children (AAP, HealthyChildren.org) (opens in a new tab) (accessed 2026-10-02)