The Difference Between Heat Rash and Sun Poisoning

"Hot and sunny" may seem like a good summer forecast—unless you get too much heat and sun. High temperatures and sun exposure can lead to skin problems like heat rash, which is a short-lived rash that resolves when you cool down, and sun poisoning, which is a severe sunburn that occurs alongside other body-wide symptoms.

Heat rash and sun poisoning are different conditions that occur in the heat.

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Heat Rash vs. Sun Poisoning

Heat Rash

Caused by heat, sweat, and friction
Symptoms are limited to the skin's surface
Looks like an inflamed, bumpy rash
Feels like stinging, prickly skin
Resolves when you get out of the sun and your body cools down
Rarely leads to complications, though they can include dehydration, swelling, and permanent skin damage

Sun Poisoning

Caused by severe sunburn
Includes body-wide symptoms like fatigue and dehydration
Looks like inflamed skin with blisters and peeling
Feels hot and painful to touch
May take days to weeks to fully resolve
Complications include body-wide symptoms like dehydration and fatigue; potential for permanent skin damage

What Is Heat Rash?

Heat rash is a rash you can develop when it’s hot enough to make you sweat. It’s often described as a stinging or “prickly” swelling.

If you sweat enough, sweat can become trapped under your skin's surface. The fluid then leaks into the surrounding tissue, resulting in pockets of swelling and blisters. These blisters form a rash that often appears on the chest, shoulders, neck, thighs, along skin folds, and anywhere else your skin rubs against clothing.

Heat rash is common in babies and infants because they have underdeveloped sweat glands. It is less common in adults but can still happen, especially in hot and humid environments.

What Is Sun Poisoning?

Sun poisoning is not a specific diagnosis; it’s the name given to severe sunburns. Severe sunburns that earn the moniker of sun poisoning typically affect multiple layers of skin, take longer to fade than a mild sunburn, and cause symptoms like:

Blisters
Fever
Rash
Red skin
Severe pain
Swelling

Anyone can get a severe sunburn, but people with fair skin are at a greater risk and can get burned with just 15 minutes of unprotected sun exposure. Some skin conditions, medications, and supplements can also increase your sensitivity to the sun.

What to Do If You Get Heat Rash

At-Home Prevention and Treatment

Treating heat rash involves cooling the body down and reducing sweating. Moving to a cooler location or sitting in a shared area can help.

Other strategies to help soothe and prevent heat rash include:

Applying a cool compress to areas like the back of the neck, underarms, or feet
Avoiding hot or spicy foods
Carrying a spray bottle to spritz yourself with water
Staying hydrated if you know it’s going to be hot and/or humid
Taking lukewarm showers or baths
Using moisture-wicking fabrics when possible
Wearing loose, breathable clothing

Symptoms to Watch For

You should see a healthcare professional if your heat rash doesn’t improve with these cooling strategies, or if you have other symptoms like:

Fainting or dizziness
Fever or chills
Low blood pressure
Muscle cramps
Nausea or vomiting
Pus draining from your rash
Rapid heartbeat
Swollen lymph nodes

In most cases, heat rash clears up once you cool down. Serious complications are rare. However, severe cases might require treatment with medications like hydrocortisone cream, calamine lotion, or antibiotic ointment.

Sun Poisoning Treatment and Prevention

At-Home Treatment

If you develop a severe sunburn, help relieve symptoms by:

Applying cool rags or compresses
Applying cortisone creams to reduce inflammation and swelling
Cleaning your skin with mild soap and lukewarm water
Drinking lots of water to stay hydrated
Taking a cool shower or bath
Taking over-the-counter pain relievers like Advil (ibuprofen) or Tylenol (acetaminophen)
Using moisturizing creams to reduce discomfort

Avoid Worsening Sun Poisoning

Things you should avoid with sun poisoning include:

After-sun products with lidocaine or benzocaine that may cause an allergic reaction
Oil-based creams or ointments that can block pores and trap heat and sweat
Peeling away loose skin
Popping or picking at blisters

Smart Sun Tips

Being outside in the sun and heat is sometimes unavoidable. However, you can take certain precautions to reduce your risk of sun-related complications:

Apply sunscreen at least 15 minutes before going outside
Reapply sunscreen every two hours—more often if you are swimming or sweating a lot
Stay hydrated if you know you will be in the hot sun
Try to avoid being in the sun when it’s the strongest—typically between the hours of 10 am and 4 pm
Try to choose a broad-spectrum sunscreen with a sun protection factor (SPF) of 30 or higher