BRITNEY SPEARS is so stressed out by her gig on “The X Fac­tor” that her psoriasis is acting up, say sources – and she’s scratching herself raw! PLUS: her relationship with DEMI LOVATO going to pieces too, say insiders.

Recent photos show the 30-year-old pop star’s left ankle and right heel are crusted over with scabby, blood­ied scales.

“Britney has had the skin condition for a long time, but it only flares up when she’s under extreme pressure,” an insider close to her told The ENQUIRER.

“Now she can’t seem to stop scratching and picking at the sores. She has a pso­riasis skin cream, but she says it burns, so she stopped using it.”

The unsightly effects of Britney’s pso­riasis were visible at the “X Factor” premiere party in L.A. on Sept. 11, and the insider says the show’s demands, espe­cially judging live auditions, are taking a toll.

“On the first night of the show aired, Britney looked great,” said the source. “But she did bite her fingernails nervously. And behind the scenes, she’s very uptight. When she isn’t on camera, Britney chain smokes and she can’t sit still.

“Having to look contestants in the eye is very hard for her. Ever since her big breakdown, Britney has also had phobias about strangers and be­ing surrounded by large crowds.”

The “Toxic” singer was admitted to a psychiatric ward after suffering a devastating breakdown in 2008, and she’s still on medication, said the insider. “The meds help Britney re­lax, and she’s able to soldier on, but inside she’s often ready to explode,” noted the source.

Adding to her anxiety, Britney’s relationship with fellow judge Demi Lovato, 20, is said to be dete­riorating.

Like Britney, the former Disney darling has struggled with mental health issues. She’s been diagnosed with bipolar disorder and has been in rehab for bulimia and cutting.

“Demi wants to bond with Brit­ney and talk about her bipolar diagnosis and rehab,” said the insider. “But Britney doesn’t want to hear any of it. She refuses to ad­mit that she has any psychiatric issues, and Demi’s openness about her own problems makes Britney jittery.

“On camera, Demi and Brit­ney appear to be the best of friends, but as soon as taping is over or between breaks, Brit­ney runs to her fiance Jason Trawick like a little kid.”

Meanwhile, a set insider says producer/judge Simon Cowell is handling Britney with kid gloves – though he did order her to stop biting her finger­nails when she’s in the judge’s chair.

“Simon knows Britney’s a ticking time bomb, and he’s watching over her like a hawk,” said the source. “He doesn’t want her to freak out.”