Healing is a sub-skill of waterbending that allows the bender to heal wounds; by using water as a catalyst, they can redirect energy paths around the body, concentrating more energy into a wounded area and allowing that area to heal at an accelerated rate. While this technique is effective on external, physical wounds, its ability to repair internal injuries and cure illnesses is more limited. The skill level of the healer, as well as the quality of the water used, also plays a role in its effectiveness. On rare occasions, waterbenders may instinctively be able to use this technique without any formal training.
After Avatar Aang ignored Jeong Jeong's warnings about using firebending without proper training, he accidentally burned Katara due to a lack of control over his flames. Seeking to soothe the pain, Katara submerged her hands in a creek, only to see the water around her hands glow silvery-blue and heal her; Jeong Jeong subsequently explained to Katara the healing abilities sometimes possessed by waterbenders. Having accidentally discovered this new ability, Katara used it again later that day to heal a burn on Aang's forearm, after his fight with Admiral Zhao.
Katara continued to use her abilities on a number of occasions during Team Avatar's travels: among other instances, she restored Jet's memories after he had been brainwashed by the Dai Li; she treated Hakoda's wounds during the invasion of the Fire Nation; and she healed Toph's feet after they were accidentally burned by Zuko.
After the Hundred Year War, Katara continued to hone her skills and eventually became regarded as the greatest master healer in the world. She passed on these skills to her daughter, Kya, who became a renowned healer of her own accord during her travels around the world. By 170 AG, male healers had become more common as well.
As Korra's waterbending teacher, Katara also passed the art of healing onto Korra, and she used it to heal Bolin's shoulder after it was injured in the third round of the Fire Ferrets' semifinal match in the Pro-bending Tournament. She used the technique once more when she healed General Iroh's injury he sustained during the Equalists' attack on Republic City. When Korra had her bending severed by Amon, she sought out Katara in order to be healed by her, but even she was unable to restore the Avatar's bending.
Healers are quite prominent in Republic City, and the best of them were visited by Tahno after his bending was taken from him by Amon. After Tarrlok fabricated evidence of a fight with the Equalists in City Hall, a healer was brought in to treat his arm, which he had used an electrified glove on to strengthen his alibi.
Following the Anti-bending Revolution, Kya used her ability to heal Bumi's head injury without the water making contact with him. Later on, when Jinora's soul became trapped in the Spirit World, Kya tried to keep her physical body alive by maintaining its flow of energy. However, after a week of sessions, she felt Jinora slipping away and turned to Katara's greater expertise in the art to keep the young airbender alive, until Jinora's spirit finally returned to her body. Meanwhile, Kya used the water found in the Spirit World to heal the unconscious Korra, Mako, and Bolin simultaneously.
While Korra was still recuperating mentally and physically from her mercury poisoning during the final stage of the insurrection of the Red Lotus, she visited Katara, who used her superior healing prowess to sense the grave internal damage the Avatar had suffered. Despite being a healing master, Katara could not relieve the Avatar's suffering, only help guide Korra through the recovery process.
In 174 AG, after sustaining injuries in an earthbending-cage fight, Korra healed her injured elbow herself by drawing normal water from the sink in a public bathroom. Following Kuvira's invasion of the United Republic of Nations, a number of healers helped the numerous homeless evacuees by manning a medic tent.
Physically, healing draws on the restorative properties of water when applied to organisms that are primarily composed of it, such as human beings. The technique is known to work on physical injuries, such as burns, lacerations, broken bones, diseases brought on by severe pollution, and severe tissue damage caused by lightning bolts. It is also able to cure mental distress and tampering.
The effectiveness of healing appears to be influenced by the water used by the bender: when using spirit water from the Spirit Oasis in the North Pole, Katara was able to save Aang's life after he was mortally wounded from being struck by lightning, though he remained in a coma for a few weeks and required follow-up healing sessions to cope with the pain and be restored to full health.
Though effective in many cases, healing cannot cure every ailment, as it was unable to heal Jet's internal wounds inflicted by Long Feng, or the complications associated with Princess Yue's birth. It has also been demonstrated that healing is ineffective on a person who has had their chi flow blocked or otherwise disrupted; Katara was unable to help a Terra Team member who had been a victim of Ty Lee's chi blocking skills, and not even the best healers could restore bending lost through advanced bloodbending, as demonstrated by failed attempts by Republic City's best healers to restore Tahno's, and Katara's to restore Korra's.
In most cases, this technique involves using healing to change a spirit's negative energy into positive energy, restoring its internal balance in the process. It is performed by encircling a spirit in water and is completed when the spirit begins to glow bright yellow, at which point the spirit dissipates or assumes a pacified form. Although the technique has been used extensively to calm single spirits, it can also be used to calm several spirits simultaneously, as both Unalaq and Korra have demonstrated. However, this technique does not work on spirit vines, and Korra's attempts to remove the vines invading Republic City caused them to re-surge even stronger than before.
In another variation, the conversion process can be used to promote imbalance, by changing a spirit's positive energy into negative energy. The mechanics of the technique remain the same, although the spirit is covered by purple light instead of gold. Unalaq claimed that this variation has the potential to destroy a human's soul.
- H indicates known ability to use regular healing.
- S indicates known ability to use spiritbending.
- By 100 AG, all known healers were female due to the dissipation of the Southern Water Tribe waterbenders and the tradition of the Northern Water Tribe that restricted female benders to learning healing practices only. Males began to practice the art after the end of the Hundred Year War, however, as male healers were present in both Republic City and the Northern Water Tribe.
- A technique similar to healing was used by an elderly shaman in 171 AG and involved the use of firebending to sense chi paths and detect spiritual energy within an individual. In contrast to the waterbending form of healing, this technique does not revitalize any cells to accelerate healing.
- Korra is the only person known to have used both the regular and spiritual forms of healing. She is also the only known Avatar to have been trained in healing.
- Healing was inspired by Reiki, a spiritual practice commonly known as palm- or hands-on-healing.
- The use of healing to treat mental strain or psychological trauma is similar to a form of therapy known as Transcranial magnetic stimulation (TMS), in which electromagnetic pulses are used to stimulate the development of new neural pathways to alleviate the symptoms of mental illnesses such as depression or post-traumatic stress disorder.