We’re continuing our mini-series on your sunscreen questions — we’ll pick up several more tomorrow and then, on Friday, address a biggie on the chemicals in sunscreens. (If you’re playing catch-up, take a gander at yesterday’s batch of Qs and As.)
These answers are from Dawn Davis, a dermatologist at Mayo Clinic. Questions and answers have been edited for clarity.
Is it possible to be allergic to the sun?
When people [talk about] a sun allergy, usually dermatologists think of polymorphous light eruption (shortened to PMLE or PLE) … which can [present as] different types of rashes. It’s most common among people who live in the northern latitudes and are Caucasian. It happens when your skin doesn’t see sun for a while — such as over the winter in Minnesota — and then all of a sudden you go on spring break. Because your skin hasn’t been exposed to UV light in a while your immune system might not recognize it, and then reacts to it. Over the next several weeks, the immune response fades away, a process known as “hardening.” But you may get the same problem the next spring or summer. You can also get something called solar urticaria, which is an actual allergy to UVA or UVB rays.
What advice do you give to people who seem to be allergic to sunscreen?
The first thing I tell my patients is to do the practical thing and use photoprotective clothing — you can get clothing that is rated using an ultraviolet protective factor, or UPF –hats and sunglasses more, and to avoid the sun during the peak hours of 10am to 4pm. If you want to use sunscreen, know that there are chemical blockers, which involve a chemical reaction between the UV light and ingredients in the sunscreen, and physical blockers like zinc or titanium, which act like a mirror. The UV light hits and then reflects off the blocker. People tend to be more allergic to the chemical kind. So look for zinc or titanium.
If you are allergic to something in a chemical blocker, it may not be the actual sunscreen — you may be allergic to a preservative, or base or fragrance. We can tell people to just shop around and avoid the active ingredient in something that you seem to react to. We also can do patch testing on a patient’s back and tell what you are allergic to, then give you a printout of ingredients that are okay.
Do you always need sunscreen, even if you’re out for a 6am run that is partially shaded?
Peak hours are between 10 and 4. But anytime you’re in the sun we recommend you wear sunscreen. Even if you’re out early in the morning or late in the afternoon you can still get UV rays, which can be reflected off water, snow and concrete.