How long can a rash last....

if it's a sun allergy? Can it last weeks, or does it usually last only a few days?  I get a rash on my arm every year. Last year I actually went to an allergist, and she basically told me all it is is prickly heat. But the other day I was driving home from work, a ten minute commute, and it was around 75 degrees. About ten minutes after I got home, my arm was bright red, and the bumps on the rash were about four times bigger than i've ever seen them. I don't think it looks like prickly heat, and I don't get it anywhere else on my body except the top of my arms where the skin is showing, below the sleeves. I guess I'm wondering if I need to go get a second opinion, more than anything. It looks like the rash in the picture in this link, but its not quite as red.


http://www.lib.uiowa.edu/hardin/MD/dermnet/sunpoisoning1.html


Thanks

Daisy

[Bhupinder Kaur, MD]

Hello,
The rash that you had sounds like solar dermatitis or solar urticaria. It is the development of hives minutes after exposure to the sun, which resolve in less than 1 hour.

Apply a good sunscreen with minimum spf 30 atleast half an hour before going out in the sun and cover your skin with cotton clothes as far as possible.You can take non-sedating antihistamines such as Cetirizine or Loratadine(Claritin) when the rash appears. Short courses of oral cortisone or steroids are taken for short periods (one to three days) to settle more severe symptoms.You may take Vitamin C along with the prescribed treatment. Vitamin C is a general anti-allergy supplement. Also apply calamine lotion and a mild steroid cream like dermacort on the rash.

In case the symptoms persist then pls consult a dermatologist.

I hope it helps.Take care and pls do keep me posted on how you are doing or if you have any additional queries.Kind regards.