Side-effect of peppermint oil:
1)Peppermint oil can cause heart burn and allergies such as mouth sores,flushing and headache,therefore it should be given in small amount to adults.
2)Breastfeeding and pregnant women should avoid peppermint during their pregnancy and lactation, as peppermint oil can cause adverse effect to their health.
3)Peppermint oil capsules are coated to prevent heart burn.If they are taken with the medicine such as antacids the coating breaks down and could increase the problem of heart burn.