Aromatherapy is generally safe. Essential oils can cause side effects, though. Some can irritate your eyes, skin, or mucous membranes in your nose. They can also cause mild allergic reactions.
If you drink some essential oils they can hurt your kidneys or liver. It's rare that people take essential oils by mouth, and you shouldn't do it unless your doctor says it's OK.
If you're new to aromatherapy, work with an aromatherapist or your doctor.