Pop star Lily Allen has suffered an allergic reaction to the green alien body paint she donned at a Halloween charity event in London on Thursday (31Oct13).

The Smile hitmaker, who has been on hiatus since 2010, stepped back into the spotlight by dressing as an extraterrestrial in a green sequined dress, leopard print tights, and body paint for the United Nations Children's Fund (Unicef) fundraiser for Syrian refugees.

However, the singer, who also performed a duet with former Take That star Robbie Williams at the event, has since broken out in a rash and has taken to Twitter.com to share news of the nasty reaction.

She writes, "It's Saturday night and I've had a bad reaction to the green paint from Halloween, my face is covered in hives."