Special Precautions & Warnings:
Pennyroyal is likely unsafe for anyone to use, but it is especially unsafe for children and people with the following conditions.
Pregnancy and breast-feeding: If you are pregnant or breast-feeding, it is likely unsafe to take pennyroyal by mouth or apply it to your skin. There is some evidence that pennyroyal oil can cause abortions by causing the uterus to contract. But the dose needed for this effect could kill the mother or cause her life-long kidney and liver damage.
Pennyroyal leaf tea seems to be able to start menstruation, which could also threaten a pregnancy.
Children: It is likely unsafe to give children pennyroyal by mouth. Two infants developed serious liver and nervous system injuries after taking pennyroyal and one infant died.
Kidney disease: The oil in pennyroyal can irritate the kidney and make existing kidney disease worse.
Liver disease: The oil in pennyroyal can cause liver damage and might make existing liver disease worse.