Ashley Olsen has had an incurable disease for years

Ashley Olsen, 28, has incurable Lyme disease, it has been reported. The actress and designer has battled the condition for several years after allegedly contracting it via a parasite bite.

A source explains to Radar Online in the US: "She's really sick. It's gotten worse. She was diagnosed in the very late stages so early detection measures weren't options for her. She's really going through it.

''When she does come to work, she looks haggard and dishevelled. And she's often moody. Ashley's having a very rough time right now,'' they added.

The disease can cause heart problems, and results in chronic pain in the joints and on the surface of the skin. 

Ashley has been notably absent from the public eye for the last three years. However, as the former child star has previously said: "I don't like to be the centre of attention anymore," many assumed that she had simply retired from the spotlight of celebrity.

On a rare outing with her twin sister, Mary-Kate, to the Met Ball in New York earlier this week, her pale and ill-looking appearance sparked concern among her fans. 

Avril Lavigne has also battled the same disease in recent times. Last month, the 30-year-old singer revealed: "I was up against a lot of doctors that told me I was crazy and that my problems didn't exist."

She went on to explain how "there were definitely times I couldn't shower for a full week because I could barely stand. It felt like having all your life sucked out of you".