The Island appears to have healing properties that cures inhabitants of defects, disabilities, and diseases. Most notably, Locke's paralysis and Rose's cancer, and because of such, both characters believe the Island can heal afflictions. Rose notes in "Lockdown" that Locke's injury will not take as long to heal as Jack and others suggest, presumably due to the healing properties of the Island.
The healing properties of the Island seem very strange, healing defects that were contracted before arriving on the Island almost instantly, but defects on the Island that aren't life threatening seem to heal slower. Mortal wounds do not seem to be cured.
You're gonna need to clean out the wound every couple of hours and keep as much weight off the leg as you can, all right? The Island will do the rest, John, all right?
The exact healing properties of the Island are currently unknown, though most inhabitants have heard or seen what the Island can do. When Mikhail addresses Naomi's punctured lung, he comments that the healing abilities for wounds are much different on The Island. Juliet also mentions that sperm counts for men living on the island are many times higher than normal, indicating that the healing properties of the Island generally improve biological processes. ("D.O.C.") Despite all this, when Locke is with Ben in the ruins, Ben says that the Island is very selective of whom it chooses to heal. ("The Brig")
The Island does not appear to heal an immediate death, such as when Shannon was shot or Goodwin impaled. Despite healing Rose's fatal cancer, it did not prevent the slow deaths of Boone and Libby. As of Season 3, Locke is the only person explicitly healed more than once. Perhaps most noteworthy, upon landing on the island he could walk after being paralyzed for 4 years.
- After being shot by Sayid ("He's Our You"), young Ben is brought to the Temple by Richard Alpert ("Whatever Happened, Happened") and is "healed" by the Island. ("Dead Is Dead")
- Ben had a spinal tumor surgically removed by Jack. For the eight days following the surgery, Ben was unable to walk and even to move his toes. When Locke arrived at the Barracks, Ben said he could feel "pins and needles" in his legs, and stand and walk with the aide of a walking stick. Around a week later, he showed Locke that he was now able to move about without the aid of a walking stick. ("Not in Portland"), ("The Brig")
- After only a few hours back on the island after the crash of Ajira Flight 316, Ben is seen removing his cast and regaining movement in his arm when preparing the outriggers with Sun. ("Namaste")
- Pinned by a tree during the sinking of the Island, Ben appeared minutes later to regain with complete mobility and seemed uninjured. ("The End")
- Daniel Faraday's memory is slowly returned to him when on island. It appears to heal exponentially faster after the flashes begin, but prior to them the process is painstakingly slow.
- On Day 1 Jack finds a grisly gash in his side, possibly from the crash. Kate sews up the wound. Later on, this wound never bothers Jack. ("Pilot, Part 1")
- Jin has been medically unable to father children. However, Sun is pregnant. Juliet confirms that Sun became pregnant on the Island, and also mentions that the sperm count of men on the Island is as much as five times higher than normal, thus suggesting how Jin could have fathered the child. ("The Whole Truth"), ("The Glass Ballerina"), ("D.O.C.")
- Kate was shot by some of Widmore's people near Widmore's submarine and had her wound sewn shut by Jack. Within hours she was able to use a rifle, dive into the sea, and made it off the Island without any visible sign of injury or discomfort. ("The Candidate") ("What They Died For") ("The End")
- Locke was paralyzed from the waist down because his father, Anthony Cooper, pushed him out of an 8 story window. However, Locke started to walk again immediately after crashing on the Island. Weeks later when Locke follows his vision to find the drug smugglers' plane with Boone, the Island seemingly takes away Locke’s ability to walk. Locke believes the Island is punishing him and demanding him to complete the task of finding the plane. After Boone is fatally wounded and Locke finds the plane filled with heroin, he no longer has trouble walking, and is even able to carry a dying Boone on his back. ("Walkabout"), ("The Man from Tallahassee"), ("Deus Ex Machina")
- Locke's leg is crushed and punctured by a blast door during the lockdown. Jack examines his leg and says that he thinks Locke's leg might have a fracture and that he should stay off it. For a short while he wears a splint Jack put on his legs and uses crutches to get around. Within a few days Locke removes the splint and abandons the crutches on the beach. ("Lockdown") ("Three Minutes")
- Locke's bite-wound on his hand, inflicted by his father, heals completely within 8 days. ("The Brig")
- After being shot by Ben, he somehow manages to get to the radio tower in an attempt to stop Jack from making the rescue call. ("The Man Behind the Curtain") ("Through the Looking Glass, Part 1")
- After allowing Ben to escape, Michael shoots himself in the shoulder. The wound heals at an abnormally fast pace. ("Two for the Road")
- Mikhail Bakunin stumbles upon Jin, Charlie, Hurley and Desmond in the jungle, several days after having been seriously injured in the sonic fence, when at that time it seemed to have killed him. He appears to be perfectly fine now. When he arrives back to the makeshift camp that the Others are living in he remarks that the sonic fence was not set to a lethal setting. ("Par Avion"), ("D.O.C.") ("The Man Behind the Curtain")
- While investigating The Looking Glass, Mikhail is shot in the chest with a spear gun by Desmond. Mikhail is rendered unconscious. Several moments later, he manages to dive underwater and swim around the station in full awareness. ("Through the Looking Glass, Part 1")
- Mikhail comments that Naomi's punctured lung should only take "about a day and a half" to heal, which, clearly, is much quicker than normal. ("D.O.C.")
- Naomi is stabbed in the back by John Locke and thought to be dead; but she is able to escape into the jungle, climb a tree, and attack Kate before she finally succumbs to her wounds. ("The Beginning of the End")
- Rose was dying of cancer and had very little time left to live. Since crashing on the Island, she’s noticed a difference in herself and believes she has been cured. ("S.O.S.")
- She questions why Jack developed appendicitis when the island healed her, confirming that she continues to believe that she is cured and no longer feels ill. ("Something Nice Back Home")
- On Day 44, Sawyer is shot on the raft (not on the Island). On Day 48, back at the Island, Jack begins treating the wound. Sawyer, at this point, is unconscious. Sawyer heals rapidly and the following day feels well enough to walk around with Kate. By Day 63, Sawyer appears fully healed and capable of looting the supply drop and brawling with Hurley. ("The Long Con") ("Dave")
- Mikhail shot Sayid's shoulder then removed the bullet, stitched the wound, and put his arm in a sling ("Enter 77"). Sayid's shoulder was completely healed by the next episode; although he was still bandaged, and he had full use of his arm. ("Par Avion")
While the above instances appear to indicate healing properties, there are other examples where people were NOT healed.
- Boone suffers a fatal injury when the plane in the jungle falls from its perch and crashes to the ground causing multiple severe impact and crush injuries. Locke carries him to the Caves where he chooses to be let go, even after an offer by Jack to save him, even to the point of giving Boone his own blood. ("Do No Harm")
- Colleen is shot by Sun and fails to recover. There was a large amount of abdominal bleeding involved. She might have been saved had a better doctor than Juliet performed the initial surgery or if the crash cart at the Hydra had been in working order. She survived with her wound long enough to be brought back by boat to the Hydra, and it is possible that the healing properties of the Island, while not saving her, prolonged her life.("The Glass Ballerina"), ("Every Man for Himself")
Donald & The Tailies
- Donald, one of the Tailies, died on day 5 from an infection of a leg injury sustained from the plane crash. ("The Other 48 Days")
- Three additional unnamed Tailies died as a result of injuries received in the crash. ("The Other 48 Days")
- Jack develops life-threatening appendicitis and has to have his appendix removed by Juliet. ("Something Nice Back Home")
- Edward Mars, the US Marshal escorting Kate back to the United States, suffers a severe injury to and has a piece of metal from the fuselage sticking out of his abdomen. He was shot by Sawyer, who accidentally perforated his lung and failed to kill him. He was euthanised by Jack as an act of mercy. ("Tabula Rasa")
- Despite dying off the island under the alias of Jeremy Bentham, Locke was brought back to the island but remained dead. ("The Incident, Part 1")
Disorders, injuries, and scars that either did not heal or may have healed normally:
- Aaron's (presumably) routine dermatitis. ("Maternity Leave")
- Ben (aka Henry Gale) is wounded by Rousseau in the shoulder on Day 57. By Day 65, in "S.O.S.", Ben’s wound appears better, but not at the same incredible rate that Sawyer was healed from the gunshot. Likewise the injuries inflicted by Sayid also seem to be healing normally.
- Charlie's scars surrounding (one under and one over) his left eye.
- Locke's facial scar over his right eye.
- Locke's stolen kidney does not regenerate. (Its absence saves Locke from dying when Ben shoots him where the kidney would have been.)
- Sawyer's hyperopia (vision problems) and the headaches it causes.
- Shannon's asthma. ("Confidence Man")
- However, it is worth noting that she only suffered one asthma attack during her time on the Island, which Jack diagnosed as anxiety or panic-induced.
- Jack mentioned her asthma was worse at that moment, when he was talking to her, because of anxiety. She still suffered from asthma, it just gets worse when she panics. Her breathing improved when Jack helped her calm down, but she was still in the midst of an asthma attack.
- Frank Lapidus is shown to be recovering normally from the injuries sustained in the Ajira Airways Flight 316 crash. ("Namaste"), ("Dead Is Dead")
Healing off the Island
- Sarah Shephard is miraculously healed after being operated on by Jack, allowing her to "dance at her wedding". ("Man of Science, Man of Faith")
- Rachel Carlson was stricken with cancer. Ben guaranteed Juliet that Jacob would cure Rachel if Juliet remained on the Island. Rachel was later cured and had a child. ("One of Us")
- Isaac of Uluru is credited with seemingly miraculous cures, though it is possible that he is a fraud. He claims to harness the energy of "certain places with great energy", and that there's different types of energy in different areas, each of which is only suitable for healing certain people. ("S.O.S.")
- Diane Janssen became very ill with cancer and the doctors had given her 6 months to live for the past 4 years during and after Kate's time on the Island. ("Eggtown")
- Carole Littleton recovered after being in a coma for several years, even though others said she had little chance of survival. ("There's No Place Like Home, Part 1")