Rad Child is a Fallout: New Vegas, Fallout Tactics, Van Buren and J.E. Sawyer's Fallout Role-Playing Game perk and a Fallout: Brotherhood of Steel skill (skills in this game work like perks do in other Fallout games). When you get any sort of radiation sickness, your health regenerates, the effect becoming more powerful with every threshold reached. However, radiation will continue to build up in your system, and can still kill you at the fatal threshold as normal.