Sometimes mum hair gets so bad not even dry shampoo can help. And poor Olivia Wilde's mop has certainly seen better days – but she's had rather more important things to do than brush her hair.

"I call this hairstyle, 'keep the kid alive'," she said, sharing a selfie on Instagram. "Products you'll need: sweat, string cheese, diaper rash cream, chewed up crayon, snot, and an enthusiastic spritz of panic."

And here's the culprit – wearing a bra on his head, obviously…

This cheeky chap is 18-month-old Otis – Olivia's first child with her fiancé Jason Sudeikis.

And the 31-year-old has revealed just what a cutie he is. "My son says goodbye to his toes every time I put his socks on," she tweeted recently. Adorable!

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