Coriander is likely safe in food amounts and possibly safe for most people when taken by mouth in appropriate medicinal amounts.
Coriander can cause some side effects, including allergic reactions and increased sensitivity to the sun. Increased sensitivity to the sun might put you at greater risk for sunburns and skin cancer. Avoid sunlight. Wear sunblock and protective clothing outside, especially if you are light-skinned.
There is one report of severe diarrhea, stomach pain, darkened skin, depression, lapse of menstruation and dehydration in a woman who took 200 mL of a 10% coriander extract for 7 days.
When coriander comes in contact with the skin, it can cause skin irritation and inflammation.
Special Precautions & Warnings:
Pregnancy and breast-feeding: There is not enough reliable information about the safety of taking coriander if you are pregnant or breast-feeding. Stay on the safe side and avoid use.
Allergies: People who are allergic to mugwort, aniseed, caraway, fennel, dill or similar plants might have allergic reactions to coriander.
Diabetes: Coriander might lower blood sugar levels. If you have diabetes and take coriander, monitor your blood sugar levels closely.
Low blood pressure: Coriander might decrease blood pressure. This could cause blood pressure to go too low in people with low blood pressure. Use cautiously if you have low blood pressure or take medications to lower your blood pressure.
Surgery: Coriander might lower blood sugar. There is some concern that it might interfere with blood sugar control during surgery. Stop using coriander at least 2 weeks prior to a scheduled surgery.