Delete rust and stain remover consisted of oxalic acid (an anti-rust agent), citric acid (a chelating agent) and microcrystalline cellulose, a very soft abrasive.
It should be noted, however, that oxalic acid is also present in more commonly consumed foods such as spinach, broccoli, brussel sprouts, grapefruit, chives, and rhubarb, among many others.
