Rosemary oil is the winner among our experts. “It has the strongest data supporting its ability to improve circulation and support hair growth, with some studies comparing it to 2% minoxidil,” Ostad said. While other oils may have some benefits to overall hair and scalp health, they lack the scientific evidence to support hair growth directly.

“Castor oil is another popular option for improving thickness because it contains ricinoleic acid, which can help condition the scalp and hair, though its benefits are more anecdotal than clinically proven,” Garshick said. Both Kobets and Ostad recommend pumpkin seed oil, which can naturally inhibit DHT, a hormone that can cause hair follicles to shrink, leading to hair loss. Regardless of what you opt for, “these oils are best used as adjuncts rather than standalone treatments,” Kobets said, adding that they “are most effective for individuals with dry scalps or as part of a weekly pre-shampoo ritual.”

“Minoxidil is considered the strongest, most effective and most well-studied topical ingredient for hair regrowth,” Garshick said, and nearly all our experts agreed. “While other ingredients can support scalp health and thickness, there is the most evidence to support the use of minoxidil,” she said.

Despite this, she and our experts emphasize that this doesn’t mean it’s automatically the best option for everyone or for all types of hair loss. “It may worsen hair on the face and other parts of the body,” Kobets said, noting that it may not be the right option for all women, especially those struggling with unwanted hair or hyperpigmentation.

“Hair grows faster when the follicles stay in the anagen, or growth phase, for a longer period,” Garshick said. “This is supported by increased blood flow to the scalp, reduced inflammation and minimizing factors that can push hair into a shedding phase.” Some of those triggers include stress, illness, hormonal imbalance and inflammation. “Treatments like minoxidil, peptides and antioxidants help stimulate follicular activity and kickstart cell proliferation while calming inflammation,” Kobets said.