Parsnips commonly contain a group of natural toxins known as furocoumarins. These are probably produced as a way of protecting the plant when it has been stressed. The concentration of the toxin is usually highest in the peel or surface layer of the plant or around any damaged areas.
One of the furocoumarin toxins can cause stomach ache and may also cause a painful skin reaction when contact with the parsnip plant is combined with UV rays from sunlight.
It is important to peel the parsnip before cooking and remove any damaged parts. The levels of toxin drop when the parsnip is cooked by baking, microwaving or boiling. Discard any cooking water. See more about Natural toxins in food