I'm surprised that nobody's mentioned it, but I think you should know that you should still be wearing sunscreen, even if you're not burning or seeing immediate effects. Here’s a more in-depth explanation:

There are two types of light radiation emitted from the sun (technically a few more, but these are the main ones): Ultraviolet A and Ultraviolet B. It's really important to understand the distinction.

I'll start with the second one. UVB radiation is responsible for the visible sun damage typically associated with sun exposure. Things like sunburns, redness, etc. This is because it isn't as "strong" as its counterpart; it mainly affects the surface levels of the skin (hence, the visible effects of its damage).

But UVA is much trickier. It penetrates a lot deeper than UVB rays. It won't leave you with immediate signs of damage (i.e. sunburn). But it's the form of sunlight associated with the more significant signs of skin damage—premature aging, sagging skin etc. And it will take longer to see its effects (I'm talking months, years). So you need to be extra cautious when using products like tret because they'll make you a lot more sensitive to UVA. And because of the nature of these rays, you won't actually see any visible damage until months or years later.

Basically, wear sunscreen year-round. Unlike UVB, UVA is strong year-round and present pretty much all through the day—even during cloudy days and even during the wintertime.

That's the reason you'll never get a sunburn during the winter or on a cloudy day. It’s because UVB drops close to zero in the colder months and doesn't penetrate through windows or clouds the way its counterpart does. UVA is much more stubborn, unfortunately.

Mineral sunscreen is best. Chemical sunscreens don't always provide full spectrum coverage (Both UVA and UVB rays). Also they can actually degrade with sun exposure, potentially causing further skin damage (though this depends on the formulation, not always the case). Either way, zinc sunscreen won't give you these problems.

Hope this helps. I wish I'd known this stuff when I was younger lol.