Sun blisters are small fluid-filled bumps that appear on seriously burned skin. They are caused by a sunburn, which is a type of radiation burn due to overexposure to ultraviolet (UV) radiation from the sun.

There are three degrees of sunburn that are based on the size and depth of burned skin. The higher the degree, the more severe the burn is.

Sun blisters are second-degree burns, which affect the epidermis (outer layer of the skin) and dermis (layer below the epidermis that includes blood capillaries and nerve endings). As such, they can be highly painful.

This article will explain the symptoms and treatments for sun blisters and when to seek medical attention.

Causes

Sun blisters are a sign of a second-degree burn resulting from prolonged exposure to the sun's UVA and UVB radiation. The severity of your burn depends on your skin type, the amount of time your skin is exposed to the sun, the intensity of the sun at the time of exposure, whether you wear protection (sunscreen), and more.

Sun blisters usually appear a few hours after sunburn occurs, but they can take up to 24 hours to develop.

Symptoms

It can take fewer than 15 minutes to get a sunburn. The type of symptoms you experience depends on the degree of burn. Without protection, your symptoms may be more severe.

Sunburn

The symptoms of sunburn depend on the depth of the burn.

Common symptoms of first-degree (superficial) burns include:

• Redness
• Swelling of the skin
• Dry, itchy, and peeling skin
• Pain

Common symptoms of second-degree (partial thickness) burns include:

• Blisters
• Deep redness
• Severe pain (usually painful to the touch)
• Swelling
• Wet and glossy skin
• Severe itch

Common symptoms of third-degree (full thickness) burns include:

• White, black, or charred skin
• No pain (due to destruction of nerve endings)
  

Sun Poisoning

Sun poisoning is not a medical term but it is often applied to an extreme case of sunburn that requires medical attention. Symptoms can include:

• Large blisters
• Headaches
• Fever
• Dizziness or confusion
• Fainting
• Dehydration
• Nausea or vomiting
• Rapid pulse and breathing

Treatment

While most cases of sun blisters can be treated at home, seek medical attention if your symptoms do not improve within a week.

Home Remedies

Common home remedies to treat sun blisters include:

• Keep moist. Keep the blistered area moist by lightly applying petroleum jelly (such as Vaseline or Aquaphor), aloe vera, or moisturizing cream. You can also cover it with gauze coated in petroleum jelly (don't use dry gauze).
• Drink extra water. Blistering skin can cause water loss. Drinking extra water prevents dehydration and assists with wound repair.
• Use a cold, damp compress. Use a compress to reduce swelling and redness in the sunburned area.
• Don’t pick or pop the blisters. This significantly increases the chance of infection and can cause damage to the skin that could lead to scarring.
• Take a pain reliever. Advil (ibuprofen) or Tylenol (acetaminophen) can reduce swelling and discomfort. Aspirin may be used, but only by adults.
• Avoid sun exposure while healing. If you need to be outdoors, wear protective clothing to cover your skin and apply sunscreen with a minimum of SPF 30.

When to See a Healthcare Provider

Seek immediate medical attention if you display any of the following symptoms:

• Blisters that cover more than 20% of your body: To prevent widespread infection, your healthcare provider will examine the extent and degree of your burn to determine the best course of treatment for your recovery.
• Fever, nausea, chills, or headaches: These are symptoms of sun poisoning. Depending on the severity of your burn, treatments may include intravenous (IV) fluids for dehydration, topical antibiotics (Neosporin, Bacitracin, Polysporin) to prevent infections, and oral steroids (prednisone) or topical steroids (hydrocortisone) to reduce pain and swelling.
• Your blisters turn yellow or red over time: This could indicate an infection that may require antibiotics.

Prevention

You should always try to avoid sunburn. Sunburns age skin cells and increase the risk of solar lentigo ("liver spots") and skin cancer. Prolonged sun exposure (especially during the summer) is associated with all major forms of skin cancers, including basal cell carcinoma, squamous cell carcinoma, and melanoma.

To reduce the risk of sun damage, avoid going out into the sun between 11 a.m. and 4 p.m., when the UV index (a calculation of the intensity of the sun's UV radiation) is at its highest.

If you have to be outdoors, apply a broad-spectrum sunscreen (protects against UVA and UVB radiation) that's at least SPF 30 and is water-resistant. Be sure also to wear protective clothing (including a hat and sunglasses) and reapply sunscreen every few hours and after swimming.

Summary

Sun blisters are a sign of second-degree burns from prolonged exposure to the sun. They can appear in a few short hours after exposure or take up to 24 hours to develop.

Symptoms of second-degree sunburn include the formation of blisters, deep redness, and severe pain. While most cases of blisters can be treated at home, seek immediate medical attention if blisters cover more than 20% of the body.

At-home remedies include drinking extra water, applying soy or aloe vera moisturizer, using a cold, damp compress, and taking a pain reliever. Sunburn ages skin and increases the risk of skin cancer, so take preventive steps to reduce your sun exposure.

A Word From Verywell

While it's best to plan ahead so you don't get a sunburn, it can happen due to unexpected circumstances. Get out of the sun at the first signs of redness. While sunburn is common, it can also be a serious condition, especially if it has reached the point of blistering.

Knowing what to do and what not to do if a burn develops can help you treat it at home and know when to seek medical help.