Psoriasis, psoriatic arthritis and diet


Neta wrote:

I’m a woman in my 70s and have broken out in a rash all over my back from psoriasis… I was diagnosed with psoriasis ten years ago … on a gluten-free diet the psoriasis mostly disappeared until now. I’ve been taking large helpings of prune juice for constipation …is this causing my itchy rash? Have you heard of any link?

Natural food chemicals called salicylates are one of the biggest problems for people with food intolerance and can be diagnosed by a trial of the RPAH elimination diet from Sydney's Royal Prince Alfred Hospital Allergy Unit

According to RPAH researchers who carried out a scientific analysis of salicylate contents of foods (1):

“We found that most fruits contained considerable amounts of salicylate. Raisins and prunes had the highest amounts.”

As well, prunes also contain natural chemicals called amines and glutamates that can also cause problems for some people.

Reader reports

Our readers say that psoriasis and psoriatic arthritis are among the symptoms that improve on the diet we support.

"the diet has helped my psoriasis and psoriatic arthritis about 95 percent. I started the diet for migraines... so it was a bonus really!" - from story [1567]

"the psoriasis on my arms is starting to heal..." - from story [463]

"symptoms that improve on diet - for me  it has been joint pain, respiratory issues, insomnia, restless legs, hives, psoriasis" - Cate from story [1493]

"at my absolute worst, with a diagnosis of fibromyalgia, chronic fatigue and IBS, with speech issues, constant headaches, psoriasis...I can easily say the failsafe diet saved my life" - from story [1273]

The salicylate connection -  Bernard suffered from psoriatic arthritis and psoriasis for 28 years:

“At times my condition was so bad that I was only able to walk about 50 metres without a rest…The psoriasis …was slowly spreading … the skin itch… made it difficult to concentrate, it used to nearly drive me mad and I was constantly scratching my back on door posts …”

Then, on a dietitian-supervised RPAH elimination diet:

“…I had achieved the impossible in only twelve weeks! The pain and inflammation were leaving me!… when I did the salicylates test ...I got very severe inflammation and pain everywhere …overall stiffness, joint swelling, nausea, headaches, flaring psoriasis which was itchy & peeling, itchy skin...”

UPDATE at the age of 84:

“ … thanks to being basically failsafe for nearly 23 years … I now have had 23 years virtually without pain – Bernard from story [601] 

What about other food chemicals?

Everyone is different. According to RPA researchers (2) almost all patients react to more than one challenge, averaging three for those presenting with urticaria, and six for those with systemic symptoms such as headaches and lethargy.  

RPAH challenges include:

  • natural chemicals: salicylates, amines, glutamates
  • additives such as colours, preservatives, flavour enhancers
  • foods such as dairy and gluten


For food intolerant people with constipation, psyllium husks (low in sals/amines/glutamates) are a safer choice than prune juice (very high in sals/amines/glutamates) - see psyllium factsheet 


Swain, AR., Dutton SP and Truswell AS. (1985). "Salicylates in foods." J American Dietetic Ass 85(8): 950-960.  PDF 

Loblay RH and Swain AR "'Food intolerance'. In Wahlqvist ML, Truswell AS, Recent Advances in Clinical Nutrition. London: John Libbey, 1986, pages 169-177.PDF 

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