I am using pure clove oil. it is Now brand, which is made using steam distillation and no chemicals. It is only around $6 for an ounce here. Most essential oils say on the bottle for aromatherapy use, as they can be dangerous if used improperly for internal use(so I guess the companies want to protect themselves for legal reasons. The Now clove oil bottle says something like- For aromatherapy use. For other uses see an aromatherapy book for dilution instructions. )For internal use they must be diluted properly, and only taken in very small amounts. For clove oil the recommended internal use is less than 5 drops well mixed in 2-4 ounces of water 3 or less times a day. One website recommends using up to 3 drops 3 times a day.


http://www.healingnaturallybybee.com/articles/anti1.php
If you decide to use essential oils internally, make sure they are pure enough for internal use(ie. not made by extraction with toxic chemicals), and that you are not taking too much of them.