RadAway

RadAway (sometimes spelled as Rad-Away) is a consumable item in Fallout, Fallout 2, Fallout 3, Fallout: New Vegas, Fallout 4, Fallout 76, Fallout Tactics, Fallout Shelter, and Fallout: The Board Game.

Background
 RadAway is a chemical solution that bonds with radioactive particles and removes them from the user's system. While Rad-X is designed to increase the body's natural resistance to radiation, RadAway is designed to be used after exposure. Purging the body of radiation takes some time to complete, and anyone using it will experience its adverse effects: it's a potent diuretic and can cause nausea, diarrhea, stomach pains and headaches. 

Variants
A packet of RadAway, reducing the player character's radiation count on use. RadAway is addictive in Fallout, Fallout 2 and Fallout Tactics. RadAway is not addictive in Fallout 3, Fallout: New Vegas, Fallout 4 and Fallout 76.

Its appearance also varies somewhat between games. Fallout, Fallout 2 and Fallout Tactics features RadAway in a translucent IV bag with a large red cross. In Fallout 3, Fallout: New Vegas and Fallout 4, it's a simple I.V. bag with " Rad Away " written on it in marker pen. In Fallout 76, it comes in a unique, branded packaging and trade dress with the RadAway logo.