Cannabis is a very safe herb, and CBD is a compound found in certain strains of cannabis. CBD increases our bodies own natural cannabinoids, by preventing their breakdown. This has a multitude of effects on regulatory processes. I have never heard of negative reactions to CBD use by any patient. It is well tolerated and safe. I always reccomend a whole plant preparation that does also contain some THC and the other compounds found in cannabis. Obviously if negative reactions occur, discontinue use.