This review paper on the safety and side effects of cannabidiol by the NCBI, for example, suggests that controlled cannabidiol administration is safe and non-toxic in humans and animals. It also does not induce changes in food intake, nor does it affect physiological parameters like heart rate, body temperature or blood pressure. Also, according to this review paper, “high doses up to 1,500 mg/day of CBD are reportedly well tolerated in humans.”
While everyone has their own unique body chemistry, it seems like the vast majority of people can ingest CBD oil without ever feeling any unpleasant side effects at all, and the remaining few will mostly likely experience only minor symptoms like stomach upset or dry mouth. Since scientists are using pure extracts from known sources, it’s likely that some consumer reports of headaches or other minor adverse reactions could be due to impurities in inferior CBD products.