Avoid ballooning problems by always properly charging (including not over- or undercharging) your LiPo battery. In addition to checking your RC for damage after a crash, inspect your battery packs as well. Continued use of a damaged LiPo battery can lead to balloon and rupture. If you observe ballooning while charging the battery, stop the process immediately. Continued charging of a ballooned LiPo battery can lead to rupture, explosion, or fire.
A ballooned battery is no longer usable. Dispose of it by soaking in salt water (in a covered container, outdoors) for several days to a couple of weeks to leach out all toxic materials and then throw out the battery -- or dispose of it according the hazardous materials/battery disposal guidelines for your community.