How to Grow Out Your Hair, According to the Experts

Whether you’ve chopped your hair and are now regretting it (we’ve all been there) or are on the other side of pregnancy and experiencing some postpartum fallout, there are ways to help your hair come in quicker and thicker. But, you have to be willing to meet your follicles halfway, giving your scalp and hair the right environment to flourish in.

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Meet Our Expert

• Helen Reavy is a trichologist, hairstylist, and founder of hair care brand Act+Acre.

• Dhaval Bhanusali, MD, is a medical and cosmetic dermatologist in New York City who specializes in lasers, scar minimization, and hair rejuvenation.

• Daniel Yadegar, MD, is a board-certified internist, cardiologist, and integrative medicine specialist.

“Hair is made of protein that originates in the hair follicle, and as the cells mature, they fill up with a fibrous protein called keratin,” explains Reavy. Each follicle consists of three layers: the cuticle, the thin outer, colorless layer of hair; the cortex, which contains melanin that gives your hair color; and the medulla layer, which you can think of as the innermost layer of hair or the marrow. “There are various elements found in hair that are used to make amino acids, keratin, melanin, and protein. The keratin in hair, specifically, is made from 18 amino acids, the most abundant being cysteine, but approximately 91 percent of hair is a protein made up of long chains of amino acids joined to one another by chemical bonds called peptides or end bonds,” Reavey explains.

According to the National Institute of Health, each hair has a shaft and a root. The shaft is the visible part of the hair that sticks out of the skin, while the hair root is in the skin and extends down to the deeper layers of the skin. It is surrounded by the hair follicle (a sheath of skin and connective tissue), which is also connected to a sebaceous gland. [And] each hair follicle is attached to a tiny muscle (arrector pili) that can make the hair stand up. There are also many nerve endings at the hair follicle, too; these nerves sense hair movement and are sensitive to even the slightest draft.

At the base of the hair, the hair’s root widens to a round hair bulb. The hair papilla, which supplies the hair root with blood, is found inside the bottom of the hair bulb. New hair cells are constantly being made in the hair bulb, close to the papilla.

“It’s the bulge, located in the outer root sheath at the point of the arrector pili muscle that is responsible for regulating the hair growth cycle,” Reavey adds. “It houses several types of stem cells, which supply the entire hair follicle with new cells.”

Hair Growth Cycle

“Hair grows in three phases,” explains Dhaval Bhanusali, a medical and cosmetic dermatologist in New York City. “The normal phases of hair growth include: the growth phase medically referred to as the anagen phase; the transition phase called the catagen phase, the hair’s resting phase after its growth period is done; and the third being the telogen phase, when your hair sheds or falls out [it’s normal to lose about 100 hairs a day, by the way!], which leads to your hair follicle becoming dormant until the cycle begins again three months later.”

What Causes Hair to Stop Growing

“So many factors can contribute to hair growth stopping, including poor blood flow and circulation, scalp health, diet and nutrition,” Reavey says. “For example, if you're low in minerals like iron, zinc, or selenium, this can have an impact on your hair growth and overall health, which is why it’s important to eat foods rich in these nutrients — especially if you’re experiencing hair loss — while making sure to get your blood analyzed to see what you're deficient in.” Off the top of her head, Reavey recommends these four foods, rich in iron, for healthy hair growth: quinoa (4.8 milligrams per 100 grams), lentils (6.5 milligrams of iron per 100 grams), cashews (6.6 milligrams per 100 grams), and pumpkin seeds (8 milligrams of iron per 100 grams).

Additionally, Reavey says stress plays a huge role, as it is related to raising cortisol levels [your stress hormone], which can impair a hair growth hormone that results in hair loss, as well as genetics, hormonal changes (think postpartum hair loss), different side effects of medications, trauma, and even certain surgeries.

Related: How to Prevent Every Type of Hair Loss, According to Experts

“Hair loss and overall health are so connected, we can’t talk about hair loss in a vacuum,” says Daniel Yadegar, MD, a board-certified internist, cardiologist, and integrative medicine specialist. “If we’re under stress because we’re not sleeping, if we’re not eating the right macro and micronutrients, and if we’re not getting the right vitamin levels and enough sunshine, all of these things really contribute to how we look and feel, and your outer appearance then becomes a representation of your inner biology.” And since all of these factors can play a role in how your hair grows (or stops growing), if you are noticing a lot of fallout daily, see a doctor. They can perform bloodwork to get a deeper look into what might be going on, which is crucial, and then they’ll advise from there.

How to Trigger Hair Growth

Reavey recommends creating healthy blood flow to the scalp by shampooing regularly, which she deems important, followed by frequent scalp treatments and head massages. She also emphasizes the importance of healthy and balanced nutrition, and doing your best to keep stress levels down, whether that’s through meditation, yoga, or box breathing where you inhale for four seconds, hold for four seconds, breathe out for four seconds, and then hold again for four seconds.

Related: Our 7 Picks For Where To Get The Best Hair Loss Treatments

Additionally, Dr. Bhanusali suggests that you talk to your doctor about the use of “over-the-counter topical ingredients, like minoxidil, which can convert hairs into the telogen phase and assist with the growth phase, using dihydrotestosterone (DHT) blockers — DHT is a sex hormone derived from testosterone that can cause miniaturization of the hair follicle and shortening of the anagen phase, but common DHT blockers, like finasteride, are used to block this from happening [you can find them in supplement and topical brands like Vegamour [which uses a natural DHT blocker found in red clover], Nutrafol [which uses a natural DHT blocker called saw palmetto as does Wellbel], or by using off-label medications, like spironolactone to trigger hair growth or tretinoin (retinoic acid), which can also help enhance the penetration of topicals for better results,” he explains.

“We also use Lower-Level Laser Light Therapy (LLLLT), as well as procedures like Platelet-Rich Plasma (PRP), where blood is drawn from the patient, it’s then placed into a machine where your platelets are separated from the rest of your blood, and then reinjected into your body with only the highest level of platelets to activate growth factors and hopefully result in the thickening of hair," he adds. "PRP and LLLT can both help, but it’s important to note they are supplementary options (and should not be primary solutions). There are certainly non-responders to both, and so the key is to have a multi-phase approach to treating hair loss.”

At-Home Treatments for Hair Growth

“I think the biggest misunderstanding for hair growth is how important it is to keep a healthy scalp; if the scalp has a build-up of dead skin cells, pollution, and products, this can all contribute to poor blood flow, starving the hair’s root of fuel,” Reavey says. She recommends a few products from her line Act+Acre.“ Using a chemical exfoliant weekly like Act+Acre’s Scalp renew to keep the scalp clean and also maintain healthy cell turnover is super important for healthy hair growth. Not to mention adding a growth serum like Stem Cell Scalp Serum or Nutrafol Serum to your routine, which can contribute to a healthy scalp and follicle health.

For androgenetic alopecia hair loss, minoxidil is the best treatment, with robust offerings from Hims or Virtue Labs; additionally, supplements from Nutrofol or Act+Acre can help promote regrowth. Lastly, regular micro-needling and red light therapy in-office [in which the LED tends to be stronger] can be supplemented at home with devices like Celluma or Currentbody.

In terms of navigating the product market, the growth-triggering ingredients Reavey recommends looking for are plant-based stem cells, minoxidil, caffeine, ginseng, and peptides. As far as topicals, Dr. Bhanusali agrees: “Many of our patients use topical prescription medications and have also had great results,” adds Dr. Bhanusali. “Whether it’s over-the-counter (OTC) minoxidi or in our own offices and with my own patients, I regularly compound prescription topicals [when you layer prescription medications for off-label usage into one medication] via a platform I helped create called HairStim. It allows dermatologists to use higher concentrations of ingredients, like minoxidil, and topical versions of ingredients, like spironolactone or finasteride. There’s also a growing TikTok trend to use topical retinoic acid to aid in hair growth, but I caution against this as the patients who use it for acne/anti-aging may have too high a concentration, which can cause more harm than good. It’s also important to note that compounded medications are off-label, and you should see a trained professional who can help curate an appropriate formula for you. Hair loss is an emotional journey, and it’s important to find an expert early in the process to give yourself the best chance of improvement.”

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