Serious burns are complex injuries, and difficult to heal.

Burns can affect almost every system in the body.

When someone is burned, fluid (liquid) leaks out of their cells and blood vessels, and this causes swelling. The swelling can be local (around the burned area) or systemic (throughout the body). The larger the burn is, the more swelling there usually is. If someone has burns on their face, their eyes may swell shut, making it impossible to open them, and swollen lips may make it difficult for them to talk. The swelling will start to go down in two to three days.

Breathing may be a problem for someone who is burned on their face or neck, or who has an inhalation injury (damage to their lungs).

Normal skin is a waterproof covering for your body. When it is damaged, body fluids leak out. Burn patients suffer huge losses of fluid, which must be replaced at once and continuously to keep their kidneys working.

Without their skin's protective layer, it is very easy for burn patients to get an infection (to catch germs), which their burn-damaged immune system cannot fight properly.

Burn survivors need to eat more than usual to help their wounds heal, often for weeks or months after their injury.

If a burn has damaged the nerves in someone's skin, those nerves will have to re-grow, which can take a long time, and their skin sensations (hot, cold, wet, dry, sharp, dull, smooth, rough, soft, hard, and pain) may be permanently changed.

When it is hot, your body must cool itself or it will overheat. To do this, the blood vessels at the surface of your skin dilate (enlarge), and also you sweat or perspire. In skin that has healed after a burn, both the surface blood vessels and the sweat glands have been damaged, so it is harder for a burn survivor to keep cool. Also, because of the changes in their sweat glands, itching and abnormal sweating are often a problem for them.

It is normal for a burn survivor to feel lots of different emotions at first, but this roller coaster of feelings doesn't last forever. Most burn survivors say that their emotions start calming down again within three months or less.

Nearly every burn survivor has trouble sleeping for some time after their injury. Itching, temperature regulation problems (being too hot or too cold), anxiety (worry), and pain can all cause restless sleep.

Skin Healing

Your body has two main ways of healing a skin wound.

When a wound is superficial (shallow),

healthy skin cells multiply (make more of themselves) and spread out across the open wound to cover it. This is called "epithelialisation".

When a wound is deeper,

with no healthy skin cells left in it, your body closes the wound by pulling the skin around the edges in toward the centre. This is called "contraction". Contraction can pull the healthy skin around the wound out of shape. It can also form tight bands of scar tissue, called "contractures", across joints (places where the body bends).

The healing of any large injury will leave a scar.

Your body has special cells, called "fibroblasts", which make something called "collagen" to rebuild injured skin. If lots of collagen is used to rebuild a skin injury, we can see it, and we call it a "scar".

Scars are stronger than ordinary skin, but they do not have hairs, sweat glands, or blood vessels. They may look shiny, and are often a different colour from the skin around them. Many things can affect how bad a scar is, including the size and depth of the injury, the blood supply to the area, the thickness and colour of your skin, and where the scar is.

Scars change as new collagen and blood are made. The way a scar changes depends as much on how your body heals as it does on the original injury or on a surgeon's skills, but they usually look worse before they look better. With time, scars soften and look more normal, but burn scars never disappear completely.

When a wound is too large or too deep for someone's body to heal itself, a skin graft is needed.

In skin graft surgery, the first step (called "excision") is to cut away any dead skin. The second step is to cover the injured area with a "graft", which is then stapled, stitched, or glued in place. Grafts are usually made using healthy "donor skin" taken from another area of the patient's own body. A graft is said to "take" when new blood vessels and scar tissue form in the injured area. Most skin grafts take successfully, but it may be several weeks or months before the grafted area heals completely, and it will form scar tissue. The place the donor skin came from can also scar.
There are different kinds of skin grafts:

Full-thickness skin grafts (FTSGs)

use all of the epidermis (the outer layer of skin) and all of the dermis (the layer below).

Split-thickness skin grafts (STSGs)

use all of the epidermis and part of the dermis. Sometimes the donor skin is meshed (tiny holes are cut in it) so it can be stretched to cover a bigger area. The good things about STSGs are that the donor site is less damaged than in FTSGs, and that it is more likely the graft will take. The bad things about STSGs are that they tend to contract more than FTSGs, they look less like normal skin (especially if they have been meshed), and they are more easily injured.

Skin substitutes

(also known as artificial skin or dermal substitutes) can be used if a badly-burned person doesn't have enough healthy donor skin left. Designed to mimic the structure and function of human skin, these advanced medical devices can be used to permanently replace lost skin (epidermis alone, dermis alone, or both).