I've had psoriasis since my early 20's (am now mid 40's). One day whilst on the school run one mum approached me and said she hoped I didn't mind but she'd noticed my skin and wanted to tell about something that had worked for her sister. She proceeded to tell me about the liver detox diet.
Prior to starting the diet my skin from elbow to wrist, knees to shins and most of my scalp was red, hot, angry and very sore / scaly (sounds hideous when put like that!) So what I did was follow as below for 2 weeks, within about 4 days the angriness had gone, soon followed by the redness - this was great encouragement to continue as the diet was very restrictive, by about 10 days in I had clear perfect patches of skin where previously it was terrible. after 14 days it was nearly clear, if a little dry - I was amazed, and I'd lost about half a stone!
What I did was cut out all
dairy
wheat
alcohol
red meat
spice
shellfish
common allergens
potato
carbs
high acidic fruit
caffeine - no tea or coffee (that was probably the hardest)
so that didn't leave me with much left to eat, a standard days diet was
Fruit for breakfast - berries, melon, apples, bananas - anything, just not too acidic.
Homemade veg soup for lunch, just simmered then blended veg with herbs for seasoning, no stock cubes or salt added.
Salmon, white fish or chicken / turkey for dinner with more veg - can be stirfried, doesn't need to be bland, oil rather than butter as no dairy is allowed
More fruit / soup whenever hungry.
Get as much organic as you can, that's expensive though so wash all fruit and veg thoroughly.
As much water as I could drink.
It sounds extreme but was well worth it - my energy levels improved massively, as did my confidence. Writing this has made me want to go again - we could do it together if you want to give it a try, a bit of support helps massively. The trick is planning in advance, cook ahead for family or leave them to it if they're capable otherwise it's easy to fall into picking.
My psoriatic arthritis was diagnosed about 6 years ago, a combination of methotrexate and cimzia is keeping it at bay, I still feel crap and drained a lot of the time though - I suspect if I can manage a detox again I'll really feel the benefit.
A GP I saw once looked at my medication and suggested I should be a vegan - I asked at my last rheumatology appointment whether there was any medical evidence to support this - he didn't seem to think it was worthy of any time at all.