fungus or psoriasis in buttocks fold

[Rondavous]

I have been experiencing rashes in my posterior fold (buttocks).  The rash becomes so serious that a crack develops at the top of the fold and the entire area from top to anus is red.  I have mild psoriasis that I have been treating for 30-years and assumed that the treatment would be a tar-based creme.  This usually quieted the problem down and it seemed to heal.  I was undergoing a physical exam at the VA and the nurse-practicioner diagnosed the problem as a fungus and to use Lotrimin or Clotrimazol cream.  I tried Clotrimazol 1% and got the same results that I got with the Tar-based product.  Once the rash develops, it just gets worse, even though I am using Clotrimazol.  It takes about a week of constant washing and applying the creme to get it quieted down.  When there is no infection, I dry the fold and apply Gold Bond Medicated Powder 2-3 times a day.  All it takes to get the rash fired up is for me to forget the wash and powder routine for a half day.  Any input on this?  Oh, yes, I am a full-time traveler and plan to see a dermatologist next week in Seattle.

[Rondavous]

thank you.

[Dr_Aparna]

Hi,
It could be an eczema present in the buttocks.The term eczema is broadly applied to a range of persistent skin conditions. These include dryness and recurring skin rashes which are characterized by one or more of these symptoms: redness, skin edema (swelling), itching and dryness, crusting, flaking, blistering, cracking, oozing, or bleeding.
Atopic eczema is believed to have a hereditary component, and often runs in families whose members also have hay fever and asthma.
Itchy rash is particularly noticeable on face and scalp, neck, inside of elbows, behind knees, and buttocks.Treatment is with a Corticosteroid ointment which will reduce the inflammation.
But with your history of Psoriasis, it would likely be an extension of that.These measures area must to reduce the recurrence rate.There are many treatments available but because of its chronic recurrent nature psoriasis is a challenge to treat.
Ointment and creams containing coal tar, dithranol (anthralin), corticosteroids like desoximetasone (Topicort), vitamin D3 analogues (for example, calcipotriol), and retinoids are routinely used. Argan oil has also been used with some promising results. The mechanism of action of each is probably different but they all help to normalise skin cell production and reduce inflammation. Activated vitamin D and its analogues are highly effective inhibitors of skin cell proliferation.
If topical treatment fails to achieve the desired goal then the next step would be to expose the skin to ultraviolet (UV) radiation. This type of treatment is called phototherapy.
ref:http://en.wikipedia.org/wiki/Psoriasis
ref:http://en.wikipedia.org/wiki/Eczema