When I practiced dermatology on Kauai, I was impressed with the large numbers of patients I saw with a distinctive photodermatitis. It was seen mostly in the months of December to May, and almost all were tourists. This reaction to sunlight followed the first few exposures of the year. After a few weeks, by history, it would disappear and would not return until the patients had been out of the sun for months and were then re-exposed. Gradually, my colleagues and I realized that this is a common problem, Indeed, upwards of 10% of the public may suffer from this.
(These images were taken from the article we published and show typical findings in typical areas.)
Sunscreens do not prevent it. They may potentiate it because they allow individuals to stay out long enough to absorb enough radiation. For prevention, graded small exposures work for most patients. That can be achieved by going to a tanning parlor three or four times before a winter or spring trip to sunny areas. These exposures should be short and are not intended to tan but to "harden" the skin to light. Most people gradually harden in their home setting since their natural exposure is graded.
Dr. Yoon Cohen, a recent medical school graduate, found a copy of the 1985 article which I wrote with Morison and Hood and you can read the pdf here thanks to her: Sun Poisoning Article.
Treatment: Cool tap water compresses for 20 minutes followed by a moderate to potent topical steroid cream for four to five days will help most patients. For more severe cases systemic steroids for four to fice days will give relief and allow a patient to enjoy their vacation or the beach. Hydroxizine affords some relief of itching. Of course, these treatments should be administered by one's personal physician.