So if Retin-A is so effective and so well studied, why isn’t everyone using it? Many dermatologists blame a lack of patient education.

“It’s one of the most misunderstood drugs,” said Dr. Kenneth Beer, a dermatologist in Palm Beach, Fla., and a clinical investigator for Allergan, the maker of prescription Avage and Tazorac. He is an Allergan shareholder. People use Retin-A too much, use it too often, experience negative side effects and give up on it too soon, doctors say.

The problem with Retin-A is that it may actually make skin look worse — with redness, flakiness and peeling — for up to eight weeks. “But by 24 weeks, patients will see dramatic, marked improvements,” said Dr. Min-Wei Christine Lee, a dermatologist in Walnut Creek, Calif..

Florida firefighter Susan Hobbs said when she first started using Retin-A, she broke out with severe acne. “I remember I called the doctor and told him I was going to stop using it because my face had never looked worse,” she said. But her doctor advised her not to give up. “And he was right,” Hobbs said. “In another couple of weeks, my skin cleared up.”

Manufacturers have come up with ways to make it more tolerable, less irritating and more effective. Brand-name prescription versions contain emollient moisturizers and have more-advanced delivery systems for getting the active ingredient into the skin. These additions are the main difference between generic Retin-A and the pricier name-brand versions (a large tube of a name brand will run about $150 versus about $80 for a generic).

But in every case, patience and common sense are required.

“You need to take six weeks to ramp up very slowly, but people will glob it on every night from the start and then call their doctor in a panic that their skin is red and peeling,” Beer said.

Doctors generally recommend using no more than a pea-size dab for the entire face. They advise using the product once every three nights (or once a week if skin feels irritated) for a couple of weeks, then every other night, eventually working up to every night if the skin can handle it.

Doctors caution that Retin-A is not recommended for pregnant women or people with rosacea (a condition that causes skin redness). They advise limiting its use with other potential irritants, like glycolic acids and vitamin C. Many doctors recommend applying a moisturizer over Retin-A (especially the generic versions) to help soothe skin, but suggest first waiting at least 20 minutes for the product to be absorbed.

—The New York Times