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I'm allergic to my sunscreen- and how I found that out

For one time I was very into studies on skin cancer, especially melanoma. They are among the most responsive cancer types to immunotherapies because they carry distinctive antigens for immune system to recognize (the first thing that drew me into the subject). They are highly-associated with UV light; the association is also determined by individual genetic background.

As asian, for example, I never worried too much about being sun-sensitive or getting skin cancer from a little bit too much sun bath. (Sidenote: my previous post touched upon some related mechanisms. )

However, "my whole world"/my skin changed since this past September- I've been constantly experiencing rashes, swell, and flaking on my face. That was really abnormal to me because my skin was never sensitive. For as long as 2 months, I had 4 reactions in total, and each time it got worse!

That was how my story began- How I finally figured out my "photo-allergy" to my sunscreen.

Stage 1: Immediately my knowledge pointed me to allergic reaction. It only happened on my face and neck so it should be contact allergy. As a result, I simplified my skincare regimen to only my trustworthy, oldie-but-goodies. FAIL- it soon developed again!

Stage 2: I started to take anti-allergy pills Allegra recommended by a friend and stopped using any face cream. I also got some hydrocortison cream from the drugstore. My skin seemed to calm down a little bit. I guess the drugs worked!?

Stage 3: I got back to my old face creams but I became really cautious that I didn't use any new ones. Now everything seemed fine- and for ONLY two weeks. The third and fourth time it hit me were too close that I couldn't even handle it. Both time I got really bad rashes and both time I spent a long time outside in the sun. I came to the conclusion- I must be allergic to UV!

Stage 4: My hypothesis was however declined by my dermatologist. When I finally went to see him and showed him my ugly selfies, he pointed out that my face rashes were not in a pattern that most sun-toxicity patients share. Upper eyelids, for instance, shielded by brow bone, should be free of rashes if UV is the cause. However, my eyelids were so red and swelled. He suspected it to be contact allergy and scheduled me to take a photo-allergen test in December.

Many of my previous self-treatment was real failure to him- my reckless conclusion of myself being UV-sensitive. And my taking Allegra, which actually targets type I allergic reaction (e.g. sniffing nose and sneezing), shouldn't do any good to my type IV allergy.

End of my story: my researcher-and-physician dermatologist gave me a lesson telling me how reckless and naive many of my previous hypotheses were. I was relieved to know that I wasn't UV-sensitive. However, it was only early November at that time and I needed to survive by myself till December to find out what I was allergic to lol.

Gathering all the info I had about my allergy- sunlight was definitely associated with my reaction but it by itself didn't cause it- I hypothesized that something I used on my face plus the sun were doing the bad. The most obvious answer was my sunscreen because many active ingredients in sunscreens were known as photo-allergen as to be activated by sun and became allergen. And I used sunscreen "to protect myself" on both days I had very bad reactions.

My photo-patch test result finally confirmed this hypothesis. (Oh, yes I stopped using sunscreen and survived till my patch test, yay!!) The evil that gave me all these pains for this fall is called benzophenone, a commonly used ingredient in about 2/3 of sunscreens. It functions by absorbing UV; but UV can also transform it as an allergen to a good population including me.

Updates: I switched to a new physical sunscreen now and life is good and hopeful again~ My painful 2015 fall actually now seems quite an experience. In the mind of my dermatologist, I definitely need more training to be a good scientist; you can develop allergy in the future to things you are comfortable with for now; and too much sun bath is never a good thing XP.

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