Lake Bell's daughter has epilepsy.

The 'Bless This Mess' actress has revealed her five-year-old daughter Nova has been diagnosed with epilepsy, which is described as a disorder in which nerve cell activity in the brain is disturbed, causing seizures.

Lake - who has Nova, as well as two-year-old son Ozgood with her husband Scott Campbell - says she's known about the diagnosis for ''a few months'', but didn't tell the public because she didn't want to ''endorse the existence'' of the disorder.

Posting a picture of her daughter on Instagram, she wrote: ''My daughter has epilepsy.

''It's taken me a few months to gather the courage to post about it because I do not want to endorse it's existence.

''I also didn't know why I should share it. Why tell a bunch of strangers? however in a time where we are so isolated I crave community. We all do. We want to be reminded we are not alone in any reality. (sic)''

The 41-year-old actress has insisted her family will ''fight for Nova'' to make sure she ''doesn't have to cry in fear'' after having a seizure, and told those who are also dealing with a loved one who has epilepsy they are ''not alone''.

She added: ''And above all, I am grateful... Grateful to have a partner in @scottcampbell who, with his research and smarts, is giving these seizures a worthy adversary. Scott and I, along with the care of the incomparable @childrensla, will conquer them. For Nova... so she doesn't have to cry in fear after she gets sucked into one. They are like invaders, that come on without invitation nor warning. We will fight for Nova. For her future. For tomorrow. For today. It's a beginning of a long journey and I want/need to remember that I am not alone. And if you are dealing with a loved one with epilepsy, I get it... You are not alone. (sic)''