So much skin care is just guesswork: you can test a certain type of retinol, for example, but you still won't know how it works for you until you actually test it. And even then, it may take a few rounds to see if it does the job or not. Sure, you might know right away if a product is causing an allergic reaction, but it often takes a few days for skincare to show signs such as clogged pores or increased oil production. "Over time [journaling] gives you a lot of clues about where your skin is really headed," says Yoon. And alternatively, what it can't stand.
If you have inflammatory skin conditions, keeping a skin care journal can help you keep tabs on flares and triggers. "When I get flare-ups, I remember it lasted longer than it actually was," she notes. "I look back at my diary and it was only three days when it felt like two weeks." This timestamp can also provide information about what else was going on in your life – stressful situations, cold weather, and the like – which could have provoked the symptoms.