A Reviewer's Month With Vitamin C Serum

We used a vitamin C serum every morning for four weeks under sunscreen, on skin that runs slightly dry and reactive in the colder months, to see whether the brightening claims held up outside a lab.

Week one brought mild tingling on application and nothing visible. By week two the tingling had stopped and morning skin looked noticeably less dull. By week four, a handful of post-blemish marks had faded faster than they usually do unassisted.

It did not work miracles, and it will not replace sunscreen or a good moisturizer — but as a five-minute addition to an existing routine, the brightening effect was real enough to keep it in daily rotation.