Exposed to the Hiroshima atomic bomb on August 6, 1945, the man's back began to develop keloids; in 1947, the Hiroshima atomic bomb burns left keloid scars on the man's back.

    Exposed to the Hiroshima atomic bomb on August 6, 1945, the men's backs began to develop keloids; by 1947, the Hiroshima atomic bomb burns had left keloid scars on the men's backs. Surviving A-bomb survivors suffered horrific keloidal burns. The extreme heat radiation burned him so badly that he developed a distinctive keloid scar. That keloid scar is larger than the initial burn. Keloids formed during the healing process of skin burned by exposure to the atomic bomb. It is irregular, abnormally protruding scar tissue. Keloids are most commonly seen in survivors within approximately 2 km of the hypocenter, and they form approximately 4 months after the bombing, followed by the greatest bulging 6 to 14 months later. Scars formed in areas where the victim's skin was directly exposed to the heat of the initial flash of the explosion. Keloids left permanent scars on the victims' minds and bodies. Those with keloids on their faces suffered great emotional distress, while those with keloids on their backs and shoulders were reluctant to show their skin. Many wore long-sleeved shirts even in summer.

　On August 6, 1945, the United States dropped an atomic bomb on Hiroshima, killing 78,000 people instantly. Those who survived suffered radiation sickness and severe burns, and the city was completely destroyed. Approximately one second after the atomic bomb was dropped on Hiroshima, a huge fireball of about 280 meters in diameter erupted. The temperature at its center exceeded about one million degrees Celsius. The heat rays from the atomic explosion can raise the surface temperature of everything it passes through to a maximum of 3,000 degrees Celsius or more. The sudden, rapid rise in temperature caused the surrounding air to expand rapidly, creating a blast that exceeded the speed of sound. The drop in air pressure in the space behind the blast created a backdraft powerful enough to rupture the eyes and internal organs of Hibakusha in its path. Most Hibakusha within about 1 km of the hypocenter were killed instantly. Hibakusha farther away were exposed to debris from city buildings.

　Most of the radiation produced by the explosion was gamma rays, and another 10% was neutron rays. Both are a type of ionizing radiation that causes changes in DNA. Neutrons were far more dangerous. About 10% of the approximately 64 kg of uranium in Little Boy, as the Hiroshima atomic bomb was called, was eaten up in the first fission reaction. The remaining approximately 90% of the radioactive material was scattered over the city of Hiroshima by the blast. As a result of that radiation exposure, many Hibakusha suffered from radiation sickness, which included vomiting, fever, fatigue, bleeding gums, thinning hair, and diarrhea. Suffering from A-bomb diseases, in the worst cases, led to death from A-bomb sickness. Those survivors who did survive were subsequently at increased risk of cancer. There is no known evidence of abnormalities in their offspring.