President Donald Trump's skin has been a hot topic of debate for years.

Recently, the internet lit up with a new question about the president's skin: what is that discolored circle on the left side of his face?

We know a bit about Trump's skin-care habits and medical conditions already. He has rosacea, a reddening skin condition that he takes antibiotics to combat. Makeup artists have also speculated that Trump's facial coloring suggests he uses self-tanner or a tanning bed. Plus, the president enjoys being out in the sun — he has logged more than 100 golf course visits during his 16 months in office, which is enough to work up a golfer's tan.

But according to dermatologist Kathleen Suozzi from the Yale School of Medicine, the barnacle-looking patch of skin on Trump's face is probably not a sun spot, and it likely has nothing to do with his rosacea or tanning regimen, either.

Suozzi needed only a quick glance at a recent photo of Trump to venture a guess: it's likely a skin growth called keratosis.

Here's her full assessment.