"It's not good for my self-esteem," she said Wednesday while in New York to open the Neutrogena Sun Summit.
The exception was after the Oscars last month. Garner's violet-colored, custom-made Gucci gown was a winner—but that wasn't what she was looking for after husband Ben Affleck's film "Argo" won best picture. "I reveled in all those good pictures of him," she said.
Garner, a Neutrogena spokeswoman, practices what she preaches when it comes to sun safety. Her children make sure of it.
In her household, sunscreen is like seat belts: non-negotiable. Garner said while she was away Wednesday, the kids surely would remind their dad if he dropped them at school without their daily slathering.
"I think I once told my kids it was against the law not to wear sunscreen," she said.
Garner's appearance was followed by a panel discussion that included dermatologists, a NASA scientist and Mexican actress Sandra Echeverria.
An eager science student growing up, Garner, 40, said the conference's terminology—and warnings—about the ozone layer and ultraviolet rays isn't lost on her. She joked, though, that she wouldn't want to be quoted on exactly what the Helioplex formulation is or what vitamin C can do for the skin.
But she had her "a-ha" moment about sun damage in her 20s, when she was out with friends. "They all had big hats on, and I didn't."
"Suddenly you look one day and the sun damage is there ... and then you see it increase exponentially."
She'll take little credit for that Oscar night look—calling it a team effort led by Rachel Zoe. The partnership between Zoe and Garner goes back more than a decade, with Garner as the stylist's first big Hollywood client.
"She knows I'm not going to wear super-crazy fashion," said Garner. Where Garner leans toward comfort, Zoe goes for fancy—and "she usually wins."
Garner's outfit Wednesday—an Oscar de la Renta sheath dress and pointy-toe pumps in black patent leather—hit the right balance. In her casual style, Garner, wearing a smile, described the look as "just a little purple Oscar number."