Spending time in the sun often feels harmless—ideal for sunbathing, outdoor fun, or beach getaways. But prolonged exposure to ultraviolet (UV) radiation can lead to serious skin damage. One common and painful result is Sun Blisters—fluid-filled bumps that indicate severe sunburn. But what exactly are Sun Blisters? How do they form, what are the symptoms, and how should you treat them? More importantly, how can you avoid getting them in the first place?

This comprehensive guide explores the science behind Sun Blisters, their causes, warning signs, treatment methods, and when to seek professional medical care.

The Basics: What Is a Sun Blister?

A sun blister is a small, fluid-filled bump that appears on the skin following a severe sunburn. Medically, these blisters are categorized as a second-degree burn. Unlike a mild sunburn—which causes redness, warmth, and peeling—a sun blister indicates that both the outer layer of the skin (epidermis) and the layer underneath (dermis) have been damaged.

When skin cells are exposed to excessive UV radiation, they become injured. This triggers an inflammatory response in the body. The immune system reacts by sending fluid to the damaged area. The fluid collects under the top layer of skin, forming a blister.

Blisters are the body’s natural defense mechanism. They serve as a protective bubble, shielding the raw, sensitive tissue beneath while new skin regenerates.

What Causes Sun Blisters?

The primary culprit behind sun blisters is ultraviolet radiation—specifically UVA and UVB rays emitted by the sun. Here’s how it works:

• UVA rays penetrate deep into the skin’s dermis. They contribute to skin aging, DNA damage, and play a role in the development of some skin cancers.
• UVB rays are largely responsible for sunburn. They damage the outer skin layers and directly cause the burn that can lead to blistering.

When the skin is exposed to high doses of UVB rays—typically due to prolonged sun exposure without adequate protection—the cells can’t repair themselves fast enough. As damage spreads, the body responds with inflammation and fluid accumulation, resulting in blisters.

A sun blister is the body’s way of isolating the injured tissue and preventing infection.

Risk Factors for Developing Sun Blisters

Anyone can get sun blisters, but certain factors increase your risk:

• Skin type: Fair-skinned individuals with low levels of melanin burn more easily. Melanin provides some natural protection by absorbing UV rays.
• Time of day: UV radiation is strongest between 10 a.m. and 4 p.m.
• Altitude: UV rays are more intense at higher elevations.
• Latitude: Closer proximity to the equator means stronger sun exposure year-round.
• Weather: Cloud cover doesn’t block all UV rays; up to 80% can penetrate clouds.
• Reflection: Surfaces like water, sand, snow, and concrete reflect sunlight, increasing UV exposure.
• Medications: Some drugs—like certain antibiotics, diuretics, and acne medications—can make skin more sensitive to UV rays, a condition called photosensitivity.

What Do Sun Blisters Look and Feel Like?

A sun blister usually develops 6 to 24 hours after sun exposure. Signs include:

• Appearance: Small, clear, fluid-filled bubbles that may cluster together. The surrounding skin is often intensely red.
• Texture: The area is swollen and tender to the touch.
• Pain: Sun blisters can be quite painful and may sting or burn.
• Peeling: Over time, the blister dries out, the top layer may peel off naturally as new skin forms underneath.

In severe cases, sun blisters can be accompanied by additional symptoms like fever, chills, nausea, or dehydration. These signs suggest sun poisoning—a more serious reaction that requires medical attention.

What Happens Beneath the Skin?

To understand why blisters form, it’s important to grasp the skin’s structure. The skin has three main layers:

1. Epidermis: The outermost layer that provides a barrier.
2. Dermis: The thicker middle layer containing connective tissue, blood vessels, and nerve endings.
3. Subcutaneous tissue: The deepest layer made up of fat and connective tissue.

A mild sunburn damages only the epidermis. A severe sunburn that leads to blisters affects both the epidermis and the upper dermis. The blister forms when fluid leaks from damaged blood vessels in the dermis and collects between skin layers, separating them and cushioning the tissue as it heals.

Should You Pop a Sun Blister?

No. Dermatologists strongly advise against popping or draining a sun blister at home. While tempting, this can expose the sensitive, raw skin underneath to bacteria, greatly increasing the risk of infection.

The blister acts like a sterile bandage. Popping it removes this protection prematurely. If a blister accidentally bursts on its own, keep the area clean and cover it with a non-stick, sterile bandage to prevent infection.

How to Treat Sun Blisters Safely

Caring for a sun blister is similar to treating a burn. Here are evidence-based steps to help your skin heal:

1. Get out of the sun immediately
Stop additional UV exposure to prevent further damage.

2. Cool the area
Apply a cool compress or take a lukewarm bath. Avoid using ice directly—it can cause further skin injury.

3. Keep the blister intact
Don’t pick at it. Let it heal naturally.

4. Moisturize gently
Use aloe vera gel or fragrance-free moisturizers to soothe the skin. Avoid petroleum jelly on large blistered areas as it can trap heat.

5. Stay hydrated
Drink plenty of fluids to help your skin recover and to prevent dehydration.

6. Use pain relievers if needed
Over-the-counter medications like ibuprofen or acetaminophen can help with pain and inflammation.

7. Cover if needed
If the blister pops, wash the area gently with mild soap and water, apply an antibiotic ointment, and cover it with a sterile bandage. Change the dressing daily.

What Not to Do

To protect your healing skin:

• Don’t scratch or peel the blister.
• Don’t apply butter or greasy ointments—they can trap heat.
• Don’t apply harsh soaps, alcohol, or hydrogen peroxide—these can delay healing.
• Don’t expose the area to direct sunlight while it’s healing.

When to Seek Medical Help

Most sun blisters heal on their own within a week or two, but severe burns can lead to complications. See a doctor if you experience:

• Blisters covering a large portion of your body.
• Signs of infection: increasing redness, pus, swelling, warmth, or red streaks around the blister.
• Severe pain that does not improve.
• Fever, chills, nausea, headache, or confusion—possible signs of sun poisoning or heatstroke.

Children, older adults, and people with compromised immune systems are at higher risk for complications and should seek medical help sooner if severe sunburn occurs.

Possible Complications

While sun blisters usually heal without problems, there are risks:

• Infection: Popped or scratched blisters can become infected with bacteria like Staphylococcus aureus. This can lead to cellulitis, an infection of the deeper skin layers that may require antibiotics.
• Scarring: Severe burns that damage deeper tissues can result in scars.
• Hyperpigmentation: The affected area may darken or lighten compared to the surrounding skin.
• Increased skin cancer risk: Repeated severe sunburns—especially blistering sunburns in childhood or adolescence—significantly increase the risk of melanoma and other skin cancers later in life.

How Long Do Sun Blisters Last?

Healing time depends on the severity of the burn and your overall health. Small sun blisters typically dry out and peel within 7 to 10 days. The underlying skin may remain pink and sensitive for a few weeks afterward.

It’s important to protect the healing skin from further sun exposure. Wear protective clothing or stay in the shade until the area is fully healed.

How to Prevent Sun Blisters

The good news? Sun blisters are preventable. The key is consistent sun protection:

• Use sunscreen: Apply a broad-spectrum sunscreen with at least SPF 30. Reapply every two hours and after swimming or sweating.
• Wear protective clothing: Cover your skin with long sleeves, wide-brimmed hats, and UV-blocking sunglasses.
• Seek shade: Stay out of direct sunlight during peak hours.
• Be mindful of reflective surfaces: Use extra protection near water, sand, or snow.
• Check your medications: Ask your doctor or pharmacist if any medications you’re taking increase photosensitivity.
• Protect children: Kids’ skin is especially vulnerable. Make sure they wear hats, rash guards, and sunscreen.

Are Sun Blisters the Same as Heat Blisters?

No—sun blisters and heat blisters are not exactly the same, though both are types of burns.

• Sun blisters result specifically from UV radiation damaging skin cells.
• Heat blisters can result from direct contact with a hot surface, flames, steam, or scalding liquids.

Both involve similar mechanisms—fluid collects between skin layers to protect underlying tissue—but the causes differ.

Myths About Sun Blisters

Myth: You can’t get sunburned on a cloudy day.
Fact: Up to 80% of UV rays can penetrate clouds.

Myth: A base tan protects you from sunburn.
Fact: A tan provides minimal protection—roughly equal to SPF 3 or less. It is not enough to prevent blistering.

Myth: Popping a blister helps it heal faster.
Fact: Popping a blister exposes raw tissue and invites infection. It should be left intact.

Long-Term Skin Health

While a single blister may heal completely, repeated sunburns can cause permanent skin damage. The skin may lose elasticity, develop wrinkles, or show uneven pigmentation. More importantly, every severe sunburn increases your lifetime risk of melanoma, the deadliest form of skin cancer.

That’s why prevention is so crucial. Sun protection isn’t just for beach days—it’s a year-round habit that protects your skin’s health and appearance for life.

Final Thoughts: Take Sun Blisters Seriously

A sun blister is more than just a minor inconvenience—it’s a clear sign that your skin has suffered significant damage. By understanding what sun blisters are and how to care for them properly, you can protect your skin and support healing.

Above all, the best treatment is prevention. Prioritize sunscreen, protective clothing, and shade. Teach children sun safety early to build habits that last a lifetime.

If you ever experience a severe sunburn that results in blistering, don’t panic—stay calm, follow proper care steps, and reach out to a medical professional if needed.

Your skin is your largest organ and your first defense against the environment. Treat it with the care and respect it deserves, and it will serve you well for years to come.

Sources

1. MedlinePlus, Sun Exposure
2. American Cancer Society, How to Protect Your Skin from UV Rays
3. NHS, Sunburn