Lily Allen has had an allergic reaction to her Halloween costume.

The 28-year-old singer's skin has broken out in a rash after she painted herself green to dress up as an alien for the spooky celebration on Thursday night (31.10.13).

She tweeted on Saturday (02.11.13): ''It's Saturday night and I've had a bad reaction to the green paint from Halloween, my face is covered in hives. I'm also sat in a Harvester.''

She then added: ''In Portsmouth. Jessie J is on the radio, suddenly everything's fine. #alltimelow''

The 'Hard Out Here' hitmaker's misery is the result of a good cause as she dressed up to attend the 2013 UNICEF UK Halloween Ball in London, where she performed with Robbie Williams to help raise vital funds for the organisation's work for children affected by the current Syria crisis.

Lily is in the midst of staging a comeback ahead of the release of her new album next year.

A lot has changed for the star since she released her last album, 'It's Not Me, It's You' in 2009, with her marrying Sam Cooper and becoming a mother to daughters Ethel, 23 months and Marnie, nine months, but she recently insisted her new album isn't a ''mum'' record.

She said: ''It's not an earnest 'I'm a mum' kind of record. It's empowering. There's some feminist vibes going on. It's the same old me with a bit of swearing going on.''