Minoxidil seems like a wonder drug for preventing hair loss and encouraging regrowth. Many people with male and female pattern baldness rave about the positive results they see from regular use. Minoxidil works. But the funny thing is, scientists aren’t sure exactly what features of minoxidil make it so effective. Here are four well-researched theories about how minoxidil impacts hair regrowth.

1. Prevents and Reverses Miniaturization of Follicles

When a person experiences androgenetic alopecia, aka male or female pattern baldness, their hair follicles begin to get narrower. This process of narrowing is known as follicle miniaturization. It’s caused by a combination of factors, including genetics and hormones. The main hormone associated with miniaturization is called dihydrotestosterone, or DHT for short.

Over time, the hair these miniaturized follicles produce gets thinner, weaker, and more prone to breakage. Eventually, these hairs start to break or fall out before they can grow to even visible lengths. When these follicles stop producing hair entirely, they are sometimes referred to as dead hair follicles. These follicles may, however, simply be in an extended resting phase.

When a person has a lot of dead or miniaturized hair follicles, they’ll see hair thinning, balding, and a receding hairline. But minoxidil may help slow, stop, and even reverse the process of miniaturization. The exact mechanism of action isn’t certain, but minoxidil seems to bring increased blood flow to the hair follicles.

With improved blood flow — and therefore more oxygen and nutrients — hair follicles begin to widen again. Wider, healthier follicles can grow thicker, stronger hair that isn’t as likely to break or fall out. With consistent, twice-daily application of minoxidil, affected hair follicles will continue to widen and produce more hair.

2. Improves Blood Flow to Hair Follicles

The previous section mentioned that minoxidil increases blood flow to the hair follicles. Let’s explore that in a little more detail. Minoxidil is what’s called a vasodilator, which means that it can help relax the blood vessels. Minoxidil is so effective at doing this that it’s also prescribed, in its oral form, to reduce blood pressure. As the blood vessels relax, they expand, or “dilate.”

Dilated blood vessels in the scalp are able to deliver a higher volume of blood to the hair follicles. This increased blood flow may play a role in stopping and reversing follicle miniaturization. It can also have an effect on the hair growth cycle, i.e. the time each hair spends growing versus resting.

This effect is thought to be because blood carries oxygen and nutrients that help stimulate the follicles to produce healthy hair. Scientists have looked at multiple nutrients in the blood that could have an impact on hair growth and hair loss. Iron and biotin (vitamin B7), for instance, can play a role in healthy hair development.

One nutrient in the blood that’s delivered to the hair follicles is called VEGF, a protein called a “growth factor.” A growth factor is a protein or steroid hormone that helps cells grow and divide to produce more cells. Growth factors like VEGF could cause hair to regrow when delivered to the follicles. Vasodilation means more nutrient-blood arrives at the follicles, which would mean more growth factors, encouraging hair regrowth.

3. Acts as a Potassium Channel Opener

A potassium channel opener is a specific type of vasodilator, which helps potassium ions move in and out of your cells. Like all vasodilators, potassium channel openers help increase blood flow and lower blood pressure. As discussed previously, this means more blood — and therefore more oxygen and nutrients — delivered to the hair follicles.

But potassium channel openers work a little bit differently from some other types of vasodilators. One of the ways they do this is by acting on certain types of smooth muscles in the body. Potassium channel openers do this by causing something called hyperpolarization. Hyperpolarization, in turn, causes muscle relaxation.

Some examples of potassium channel openers are drugs including cromakalim and nicorandil. Minoxidil is also understood to be a powerful potassium channel opener. In certain types of primates, all of these drugs have been shown to stimulate hair growth. For humans, these medications are usually prescribed to help lower blood pressure.

Some of what scientists know about hair loss medications actually comes from unintended side effects seen in blood pressure patients. Hair regrowth has been observed in patients taking certain medications for their blood pressure, including potassium channel openers. (These types of unexpected medical results are common. In fact, minoxidil itself was originally invented to — unsuccessfully — treat ulcers.)

4. Alters the Hair Growth Cycle

Minoxidil can also work by shortening the duration of the telogen, or “resting” phase of hair growth. During the resting phase, hair stops growing, and more or less hibernates for up to three months. Minoxidil can speed up the telogen phase and kickstart the phase that follows: the growth phase. Scientists think it does this by stimulating the secondary germ — the outer layer of the follicle.

When the telogen phase goes faster, some people experience shedding of their finer, thinner hairs. This causes some minoxidil users to panic, incorrectly believing the product is actually making their hair loss worse. In fact, losing these weaker hairs is a good thing. It means healthy, thick hair will likely grow back in its place in just a few more months.

After the telogen phase, the next phase is called the anagen or “growing” phase of the hair cycle. Not only can minoxidil make the growth phase start sooner; it can also make it last longer. Normally, an anagen phase lasts somewhere between two and six years. But researchers think — though it hasn’t been proven yet — that minoxidil prolongs this timeline.

Minoxidil may extend the anagen phase by slowing down cells’ aging process. Instead of getting older and dying off, the cells in hair follicles continue to grow. When hair follicles are in the growth phase, hairs usually grow about an inch every two months. This means each month spent in the growth phase is a big step toward a full, healthy head of hair.

Consistent Use for Longer and Stronger Hair

Researchers are still learning more about the science behind what makes minoxidil work so well. But what they do know for certain is that minoxidil really could help give you the regrowth results you want.

Minoxidil is available in foam and solution forms, which you apply by simply rubbing the product into your scalp. Remember to use minoxidil every day, at the recommended dosage, and stay consistent over time. Minoxidil stops working when you stop using it, so try never to miss an application.