The Smile star shared a shot of her daughter with wet hair on Instagram and revealed she's going through every mum's worst nightmare - her kid has nits.

She simply captioned the snap "Nits".

It's not clear if the girl in the photo, with her back to the camera, is Lily's four-year-old Ethel Mary, or three-year-old Marnie Rose - her kids from her marriage to estranged husband Sam Cooper.

The singer recently returned to social media after announcing she was taking a break from microblogging in August (16) to focus on time with her children as they prepared for the school year.

She also put the release of her new album on hold, announcing in a final pre-hiatus tweet: "(I) have postponed delivery (of my new album) because I want to be on hand to settle my daughter into big school this Sept (September)."

The move came shortly after photographers caught intoxicated Lily collapsing at London's Notting Hill Carnival. She was carried out of a party by her boyfriend Meridian Dan.

She first returned to social media over the weekend (23-25Sep16), tweeting about hit new Netflix series Stranger Things. Allen also posted a shot of herself on Sunday (25Sep16).

Lily has over 800,000 followers on Instagram.