I have been to the Blue Lagoon and was impressed - my psoriasis was in remission at the time, so I did not do any specialized treatments - just bathing in the silica rich warm waters. Very nice.

Have also talked with some people that went to the Dead Sea spa, and they experienced some improvements. They attributed it mostly to the UV light exposure.

I personally think that the leaky gut hypothesis explains much of my psoriasis - although genetics and infectious disease also play a factor. Oatmeal, slippery elm and other foods/herbs to coat the gut and reduce absorption of large protein allergens, turmeric and other anti-inflammatories to calm the immune system. That's what works best for me - your mileage may vary.

Here is a link that might be useful: Iceland's Blue Lagoon for Psoriasis