Yes, its safety when used as a food additive has been approved by the U.S. Food and Drug Administration (FDA), European Food Safety Authority (EFSA), Joint FAO/WHO Expert Committee on Food Additives (JECFA), as well as other authorities.

FDA
The FDA claimed guar gum added directly to human food affirmed as generally recognized as safe (GRAS) (6). And it is also safely used as a stabilizer in animal feeding. (7)

It can be used as an anticaking agent, emulsifier, stabilizer or thickener and with other functions in food. (8)

The following food may contain guar gum and with the maximum use levels (9):

Processed vegetables and vegetable juices: 2.0%
Fats and oils: 2.0%
Breakfast cereals: 1.2%
Gravies and sauces: 1.2%
Sweet sauces, toppings and syrups: 1.0%
Dairy products analogs: 1.0%
Jams and jellies: 1.0%
Soups and soup mixes: 0.8%
Cheese: 0.8%
Milk products: 0.6%
All other food categories: 0.5%
Baked goods and baking mixes: 0.35%

http://www.chinafooding.com/Guar_Gum