No one knows exactly what causes it... or why it can sometimes engulf your whole body.
But for anyone living with a chronic and incurable skin disorder� not a day goes by without wanting to take refuge from the pain, the suffering and the humiliation.
John O'Neal is a proud father of four and holds a steady job as a sales guru. This otherwise confident man is the first to admit he doesn't feel comfortable in his own skin.
"I haven't worn shorts or a short sleeve t-shirt in a long time, you know years."
"Do you feel in a sense you've lost some of the best years of your life? I think so, especially with� I've got 4 young children so we don't go to the beach very often, I don't go to the public pools," says John.
I'd wake up in the middle of the night and my hands would be covered in blood from scratching.
Diagnosed in his late teens with psoriasis, he was told by doctors it was probably brought on by stress or an over active immune system.
"I first noticed in 1996/1997 and it was a little spot on my head and I scratched it and it went away and it came back again and by about 6 months later the patch was probably so big," explains John.
Over the years it continued to proliferate to the point now where it covers nearly 80 percent of his body.
"From what doctors have said it's probably one of the worst cases for severity in Adelaide that they've seen� I wouldn't wish it on my worst enemy either. This is a disease," says John.
And how about 9 year old Monika Roberts� just a few months ago a popular and carefree Adelaide youngster.
Mum Gisella says "I mean she's very self conscious about sitting on chairs at school, because it ends up flaking a lot."
"I close the door and sometimes I put long sleeves on because we go out shopping and some people stare at me," adds Monika.
Now her psoriasis is so severe, her hair often falls out and mum Gisela says she's often too ashamed to go to school.
Both tried and failed countless treatments from conventional medicine to natural therapies� UV therapy to tea gel but nothing appeared to work� until now.
John's dermatologist put him on to a new drug in the fight against psoriasis called Remicade.
John explains, "�it's fairly potent and one of the main side effects is it suppresses your immune system so you tend to get a bit sick� colds and flu and things like that, hard to fight infections so you just have to watch that."
But john is prepared to take the risk.
After just two courses of Remicade which is administered over several hours through an IV drip at the Royal Adelaide Hospital, he's seen a dramatic improvement.
"People at work they're great and my wife they're like 'oh I can't believe how good it is! And not to have it on my hands where customers can see it and things like that that's the best part," says John.
Dr Cathy Reid, Head of Dermatology at the RAH says while she's encouraged by the results so far, it's only available for severe cases who've failed all other treatments.
"The new drugs are making a difference to patients with very severe psoriasis and we're hopeful that these responses will be long term," says Dr Reid.
Unfortunately, because the drug is so potent, Remicade is a no- go for young Monika� and while she may have an agonising wait, the benefits of the drug aren't just limited to psoriasis sufferers.
Just 3 years ago... 29 year old Neil Goldsmith was at the point of despair.
"I felt as though I was dying when I had the condition. I felt as though I was near the end. I thought about suicide a lot during that time but I kept thinking that eventually I'd be dead and I'd be out of pain," says Neil.
The former martial arts whiz and athlete was struck down with Ankylosing Spondilitis or A.S.... A debilitating disease which affects the spine and joints.
As a result Neil was virtually addicted to anti- inflammatories and if that wasn't bad enough he also developed Crohn's Disease.
"My blood results showed that my blood cells weren't even the right shape, they weren't the normal kind of doughnut shape they were all rounded and they were all stuck together," explains Neil.
Thankfully he found out about Remicade and qualified for treatment alongside John at the R.A.H.
And three years down the track? "Oh I feel awesome like 95% of my pain is gone especially that acute pain� I can exercise without pain I can sleep without pain it's just amazing going to bed now is an awesome feeling now for me like in the past it was a nightmare because I knew I'd be there for hours in pain rolling around just in absolute agony," says Neil.
John too feels like a new man. For the first time in 6 years he's comfortable wearing a short sleeve shirt and has plenty of time to play outdoors with the kids.
"It's been what just over 3 weeks now and it's just phenomenal. I do I call it the miracle drug and I mean that because it is, it's a life changing experience," says John.
The criteria for acceptance by medical practitioners for use of Remicade is restrictive. For more information consult your GP or specialist.