Allergic reaction or what

  I am writing in regards to my nine year old son who has a rash between his legs closer to his knees.  It is on one side and really gets irritated when he gets it wet in the shower.  It has now started to appear lightly on the other side.  He is complaining more about it.  He also had an outbreak of hives today and had to give him Benadryl the rash thing has been going on for a couple of weeks and have a doctor's appointment tomororw> I would just like another opinion on what it might be

[HFHS.MD-HSW]

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Dear Missy:
The diagnosis of a rash depends upon several features: 1) primary lesion (flat, solid bumps, fluid-filled bumps, ...); 2) secondary lesions (scales, crusts, fissures, ...); 3) color (pale, pink-red; dark brown, ...); 4) origin, progression and final distribution (where did it start and wind up); 5) arrangement(linear, oval, ...). Your note does not address many of these features. However, the fact that getting the rash wet makes it more uncomfortable suggests a form of irritant or contact dermatitis. The developing symmetry is an important clue. If the rash itches a great deal one must consider atopic dermatitis/eczema as well, although the distribution is atypical.
This information is offered for educational purposes only. I would be interested in hearing a bit more about the outcome of the visit to the doctor.
HFHS.MD.HSW
Key Words: atopic dermatitis, contact dermatitis