"One should always test a concealer out in the store. Most places have testers where you can try the concealers before choosing one," says Dr. Debra Jaliman, a board-certified NYC dermatologist, assistant professor of Dermatology Icahn School of Medicine at Mount Sinai, and author of the book Skin Rules: Trade Secrets from a Top New York Dermatologist.
"Some people have sensitive skin or have skin conditions such as acne
and rosacea, and certain concealers can aggravate those conditions," she says, so it's best to be careful before purchasing aimlessly.