I urge everyone to bookmark that blog; it is always a fascinating tour of the weirder and wonderfuller places on our planet. And let me leave you with this simply jaw-dropping video of undulatus asperatus in action.
(A sunscreen with a physical block like titanium dioxide or zinc oxide can be applied last, after a serum or moisturizer.) Apply a serum next and, finally, moisturizer if you need it. Polis also recommends serums or sunscreens with moisturizers built in because they save time.
The right time to use a serum depends on the formula and your skincare routine. A serum can be applied in the morning, at night or both, but Dr. Charles advises against applying a serum in the evening time if you are already applying a topical retinoid. The combination of the two products may lead to irritation.