Pine needs to be kiln dried to be chin safe, raw pine contains toxic phenol that are given off as vapor, as well as the pine sap and pitch is poisonous to chins.
However if you meant untreated kiln dried pine, rather then raw pine, then it's safe.
Kiln drying heats the wood slowly to very high temps (above 60C/140F) which kills off any bugs and/or fungi inside, sets the pitch and dries out sap, as well as vents off the majority of the phenol, making the wood safe to use.