Sun rash on upper thighs?

I have medium (Asian) skin which has always tanned easily without any burning.  Two years ago I moved to a new apartment in upstate NY and developed a rash on my upper thighs after sunning at the apt. pool.  I chalked it up to a plant allergy (something growing near the pool) until the same rash reappeared a year later on a cruise.
The rash is limited to my upper thighs on the front (stops abruptly when skin is covered by bathing suit- clear lines) and behind my armpits (shows from the back, is not in the pit itself).  I had purchased new sunscreen (15 and 30) and it was even a different brand.  These are the only 2 places the rash appears.  It starts out red and painful (like sunburn) but quickly becomes hard, bumpy, scaly, peeling, especially if it is irritated (ie, wearing clothes, further sun exposure, etc).
I have ruled out (I think) the sunscreen, my bathing suit, detergents/soaps/lotions/etc.  I have been on birth control (generic Alesse) for years, before this started. Could it be a delayed reaction?

[Alan Rockoff, MD]

Not sure, but allergy to soap, detergent, product, or plant all seem unlikely.  Atopic dermatitis (eczema) is a hereditary sensitivity which can do what you say has been happening.  This is genetic, though you may be unaware of who in your family had it.  Treatment is straightforward--topical anti-inflammatory creams, steroidal or otherwise.  I advise a dermatology visit for proper diagnosis and appropriate treatment.

Take care.

Dr. Rockoff

[wasliche]

I found some pictures and information on the internet and it doesn't really sound like the same thing.  The pictures look very different.
Also this has only developed in the past 2-3 years (early twenties) which doesn't seem to follow the general trend of eczema developing in infancy/childhood.
Any chance it's just a weird reaction to the sun?  I don't know *why* I would have suddenly developed this, though

[daisy_am3]

I think I may have the same condition.  Can you describe your condition a little more clearly and do you have any photos available.  I have had a reddened rash on my upper thigh that was overly exposed to the sun since age 13.  It has gotten worse through repeated exposure and seems to be worse in the winter months.