Cinnamon is well tolerated, though the volatile oil can cause a skin rash.
Cassia and other cinnamons contain small amounts of coumarin; blood-thinning and liver problems generally occur with this compound only if large amounts are taken over long periods.
To be safe, caution is advised for anyone with liver problems.
Due to its blood-thinning effects, people should stop taking cinnamon in quantities greater than use as a spice at least one week prior to surgery.
Medicinal doses are not recommended during pregnancy.
Close monitoring of blood sugar levels in diabetics is warranted to avoid unsafe lowering of blood sugar.
