According to Dr Lowe, it’s best to start with a 0.3% strength retinol and to use a small amount every other night for a couple of weeks to see how your skin reacts. "Then you can use it nightly once your skin tolerates it," says Dr Lowe. "It's best to apply retinol products at night since the ingredient can cause sun sensitivity, so always wear SPF during the day," he advises. Once your skin can tolerate 0.3%, you can then move up to a higher strength if you want to. "But really, if you find a strength that achieves the results you like, there’s no need to go higher," Dr Lowe adds.