If fennel is edible, why is the essential oil from seeds toxic?

It is said that seeds, leaves, and roots of fennel are safe and edible. However, the essential oil, extracted from the seeds, is toxic even in small amounts. This seems to be a contradiction. Is it safe to eat seeds, or any part of the herb? if its oil is toxic?If fennel is edible, why is the essential oil from seeds toxic?
All essential oils can be toxic if ingested in large doses. Distributors of essential oils always need to mention this to be safe, CYA, you know...


It is a phenol and members of this class can be toxic, I won't go into the chemistry here. But...Fennel essential oil from Foeniculum vulgare var. dulce is not considered to be toxic. It is widely and safely used.If fennel is edible, why is the essential oil from seeds toxic?
This is a question of concentration. To take the essential oil from a seed, it could take thousands of seeds to create even a fluid ounce of the essential oil. Basically to have a little bit of the oil is like eating thousands of seeds, and a few seeds may be alright but thousands could be toxic.