Toss your stereotypical notion of the balding middle-aged man out the window. According to the American Hair Loss Association , about 40% of hair-loss sufferers are women. And many different factors can contribute to female hair loss, such as extreme stress, inflammation, menopause, and chronic conditions.To help, brands have been developing treatments that stimulate hair growth. You've probably heard of Rogaine (yes, there's a product for women ), and it's possible your hairstylist has mentioned Biotin supplements. But how effective are these treatments? And who should be using them? Ahead, we ask experts to shed some light on the subject.Before scrolling, an important note: Charlene Deegan-Calello, executive director of new product development for Keranique , stresses that you should always first identify the kind of hair loss you have before choosing a course of treatment. "There's a multitude of reasons for hair loss. If you have a stressful event in your life — and it can even be a hormonal fluctuation — or your diet's poor, that will mitigate itself," she says. "None of the follicles will shut down and your hair will regrow in the same manner that it grew prior to that event. So, for that type of hair loss, you don't need treatment at all."This kind of transient hair loss, Deegan-Calello explains, is most prevalent in younger women in their 20s and 30s. Older women, however, might have to adopt a more proactive approach. "Post-menopausal [hair loss] is different. Your hormone levels have modified and, in fact, you're producing far less estrogen," she says. "So, in that circumstance, that's when you start to see diffused hair loss — where you'll have thinning patches. It's not regrowing, typically, once you're in that stage." And then there are those with hair loss on the clinical end of the spectrum, who have a diagnostic or chronic condition.Overall word to the wise: "If you are experiencing hair loss for more than a month, go see a professional," says New York dermatologist Francesca Fusco , MD. "Anything that's going wrong can typically be corrected, [and] you want to do it before you've lost 10, 20, or 30% of the hair on your head." It's worth noting that for all of the treatments, results differ from person to person. So, whichever hair-growth path you choose to go down, get informed first.