There are four widely recognized degrees of burns, ranging from minor surface damage to injuries that reach muscle and bone. The traditional first-through-fourth-degree system is still commonly used, though medical professionals now prefer a newer naming convention based on skin depth: superficial, partial-thickness, and full-thickness.
The Four Degrees, Explained
Each degree reflects how deep the burn penetrates into your body’s tissue. The deeper the burn, the more serious the damage, the longer the recovery, and the greater the likelihood of permanent scarring.
- First degree (superficial): Only the outermost layer of skin is affected.
- Second degree (partial-thickness): Damage extends into the second layer of skin, the dermis.
- Third degree (full-thickness): All three layers of skin are destroyed, including the fat layer beneath the surface.
- Fourth degree: The burn goes beyond skin entirely, reaching muscle, tendon, or bone.
Some older references mention fifth- and sixth-degree burns for injuries that expose or char bone, but these classifications are rarely used in clinical practice. Fourth degree is the highest category most burn centers work with.
First-Degree Burns
A first-degree burn looks like a red or reddish-brown patch of skin that feels warm and painful. There are no blisters, and the skin stays dry. If you press on it, the area temporarily turns lighter before the color returns. A sunburn is the most familiar example.
Because only the top layer of skin is involved, these burns heal within 7 to 14 days and almost never leave a scar. They don’t require medical treatment beyond basic care at home.
Second-Degree Burns
Second-degree burns are split into two subtypes, and the distinction matters because one heals on its own while the other often needs medical intervention.
Superficial partial-thickness burns damage the outer skin layer and the upper portion of the dermis beneath it. These are the burns that blister. They’re painful, pink, and moist-looking. Most heal within three weeks, and scarring tends to be faint and fades over time.
Deep partial-thickness burns reach further into the dermis, damaging blood vessels, sweat glands, and hair follicles along the way. They may appear more pale or mottled than the superficial type, and they’re slower to heal. Without proper treatment, deep partial-thickness burns scar heavily and sometimes require skin grafting.
The line between these two subtypes can be hard to judge in the first day or two. Burn specialists sometimes reassess the injury 48 to 72 hours later once swelling stabilizes and the true depth becomes clearer.
Third-Degree Burns
A third-degree burn destroys all three layers of skin: the epidermis, the dermis, and the fat layer underneath. It also wipes out nerve endings, sweat glands, and hair follicles in the area. The skin looks leathery, dry, and discolored, often white, black, or a deep waxy red.
One detail that surprises people: third-degree burns are often painless at the burn site itself. The nerves that transmit pain signals have been destroyed. You may still feel intense pain around the edges, where the tissue transitions to less-damaged second-degree injury, but the center of the burn can be numb.
Third-degree burns take more than three weeks to heal and cannot regenerate normal skin on their own. The body fills the gap with scar tissue instead, which is why skin grafting is the standard approach. Without surgical repair, the scarring can be severe enough to limit joint movement if the burn crosses a joint.
Fourth-Degree Burns
Fourth-degree burns extend beyond the skin entirely, damaging the deeper structures underneath: muscle, tendons, blood vessels, nerves, and sometimes bone and joints. These are life-threatening injuries that require specialized surgical care. Skin grafting alone isn’t enough because there’s no viable tissue bed left to graft onto. Treatment typically involves removing destroyed tissue and may require reconstructive surgery over multiple procedures.
How Burn Size Is Measured
Depth tells only half the story. The other critical factor is how much of the body’s surface a burn covers, expressed as a percentage of total body surface area (TBSA). Doctors estimate this using the “Rule of Nines,” which divides an adult’s body into sections that each represent roughly 9% of the total surface. The head and neck account for 9%, each arm for 9%, each leg for 18%, and so on. A quick shortcut: the palm of your hand, fingers included, equals about 1% of your body’s surface area.
These two measurements together, depth and surface area, determine how a burn is treated. A partial-thickness burn covering 10% or more of your body generally warrants referral to a specialized burn center. Any full-thickness burn, regardless of size, calls for the same level of care. Burns on the face, hands, feet, genitals, or over joints also get flagged for specialized treatment because of the higher risk of functional problems during healing.
Immediate First Aid for Burns
For a burn that doesn’t require emergency care, the most important step is cooling it with running water that’s cool but not cold. Hold the burned area under the tap for about 10 minutes. Cold water or ice can actually worsen the injury by constricting blood vessels and deepening tissue damage in the area. After cooling, cover the burn loosely with a clean, non-stick bandage.
Any burn that looks white, leathery, or charred, or that covers a large area, or that involves the face, hands, or joints, needs professional evaluation. The same goes for chemical burns, electrical burns, and any burn in a child under 14. Burns in children are routinely referred to specialized centers because of the complexity of pain management, wound care, and screening for non-accidental injury.