Although concerns have been raised about the possible cancer-causing effects of estragole, a component found in variable amounts in basil volatile oil, small amounts of basil would not seem to pose a significant threat.¹⁸ However, because some herbal books suggest that estragole may be potentially carcinogenic and has been thought to stimulate uterine contractions, some herbal experts feel it may be best for pregnant or breast-feeding women to avoid use of the herb, especially the volatile oil.¹⁹ People with serious kidney or liver damage should not use basil volatile oil internally, as they could theoretically have trouble eliminating it from their bodies. However, use of basil as a seasoning in food is unlikely to be of concern.