Medically reviewed by Kristin Hall, FNP
Written by Our Editorial Team
Last updated 2/23/2022
If you’ve ever spent time researching hair loss, you’ve probably heard of dihydrotestosterone, or DHT.
The main hormone involved in male pattern baldness, DHT can attach to receptors in your scalp and damage your hair follicles. Over time, this can lead to a receding hairline, hair thinning and even severe hair loss.
Many hair loss treatments are advertised as “DHT blockers” -- products that either cut down the levels of DHT in your body or inhibit the effects of DHT at the scalp level.
DHT blockers can vary hugely in terms of quality and effectiveness. While some are backed up by high quality scientific research, others aren’t supported by much at all.
Below, we’ve explained how DHT can contribute to hair loss, as well as how DHT blockers work to treat issues such as male pattern baldness. We’ve also talked about which DHT blockers are worth using as hair loss treatments and which are best avoided.
DHT, or dihydrotestosterone, is a type of androgen, or male sex hormone. It’s the most potent androgen that’s produced by your body. Experts consider DHT to be a pure androgen hormone, as it can’t convert into estrogen.
Your body produces DHT as a byproduct of testosterone through the action of an enzyme called 5-alpha-reductase.
Like other androgens, DHT is highly important for your development as a male. During the fetal development process, it plays a key role in producing your male genitalia. During childhood and puberty, DHT is responsible for your body hair, facial hair, deep voice and other male features.
In short, DHT is one of the hormones that makes you, as a man, male, at least during the early phases of your life.
As an adult, DHT has less of an impact on your physical development. However, it can attach to receptors in some parts of your body, including your sebaceous glands (the oil-producing glands in your skin), your prostate and your scalp.
When DHT targets the sebaceous glands, it can increase the production of sebum (a natural oil that’s secreted by your skin) and contribute to acne breakouts. When it attaches to receptors in the prostate, it can cause benign prostatic hyperplasia (BPH, or prostate growth).
Finally, when DHT binds to receptors in your scalp, it can cause your hair follicles to go through a process called miniaturization, which eventually leads to pattern hair loss.
Healthy hair follicles go through a multi-phase process to produce new hairs, which is referred to as the hair growth cycle.
The first phase of the hair growth cycle is called the anagen phase. During this phase, the hair follicle actively produces new hairs. Most scalp hair follicles stay in the anagen phase for two to six years, during which the hair grows to its full length.
The anagen phase is often referred to as the “growth phase.” Around 85 to 90 percent of your hairs are in this phase of the growth cycle at any given moment.
The second phase of the hair growth cycle is the catagen phase. During this phase, new hairs stop actively growing and begin to thin in diameter. A bulb of keratin develops at the root of the hair, cutting off the hair’s blood supply and resulting in the development of a club hair.
The third phase is referred to as the telogen phase. During this phase, the hair follicles enter a resting state in which growth completely ceases. Around 10 to 15 percent of your scalp hairs are in the telogen phase at any time.
The fourth and final phase of the hair growth cycle is the exogen phase. During this phase, the club hair fully detaches from the scalp, allowing it to shed as new hair grows from the follicle to replace it.
So, how does DHT affect this multi-phase cycle? When DHT binds to receptors on hair follicles, it causes them to go through a process called miniaturization, in which the anagen phase of the growth cycle becomes progressively shorter.
This reduced anagen phase results in hairs that are thinner and shorter. Over time, as each hair follicle goes through a shorter anagen phase, new hairs eventually become so small that they’re unable to penetrate through the skin.
This type of hair loss is referred to as androgenetic alopecia, or male pattern baldness. It tends to begin as mild thinning around your hairline. Over the course of years or decades, it may affect your crown, eventually causing significant hair loss across most of your scalp.
Not everyone is equally sensitive to the effects of DHT, which is why some men go bald early in life while others maintain a full head of hair well into old age.
Researchers believe that men affected by androgenetic alopecia tend to have higher levels of the 5-alpha-reductase enzyme, which converts testosterone into DHT, as well as an increased level of androgen receptor activity in the scalp.
Our guide to DHT and male pattern baldness goes into more detail about what DHT is and the effects it can have on your hair follicles.
Now that you know about DHT and what it can do within your body, it’s easy to understand why DHT blockers are a thing.
DHT blockers come in two main forms. Some, such as the hair loss medication finasteride, stop DHT from being produced from testosterone by blocking the effects of certain enzymes, such as 5-alpha reductase.
Others, such as DHT blocker shampoos, conditioners and hair oils, work by blocking the effects of DHT at specific parts of your body, such as the scalp.
So, do these DHT blockers actually work? The answer to this question largely depends on your definition of effectiveness.
If you’re expecting DHT blockers to magically reverse the effects of male pattern baldness, then no, they don’t. With the exception of hair transplant surgery, there’s no way to instantly restore a receding hairline or other consequences of pattern hair loss.
However, if you have realistic expectations and want to stop, slow down or partially reverse the effects of male pattern baldness, then some DHT blockers -- the ones supported by high quality scientific evidence, at least -- are definitely worth adding to your hair loss prevention routine.
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When it comes to treatments for hair loss, not all products are supported by an equal amount of scientific evidence.
This is especially true for DHT blockers. While some, such as finasteride, are backed up by lots of high quality, unbiased research, others are aggressively promoted without much in the way of evidence to support their supposed benefits.
Because of this, it pays to be picky when it comes to DHT blockers. Stick to treatments that are backed up by real, large-scale research, and try to ignore those that make ambitious claims that aren’t supported by the facts.
By far the most effective DHT blocker on the market is finasteride, a prescription medication that is approved by the FDA for treating male pattern baldness.
Finasteride belongs to a class of drugs called 5-alpha-reductase inhibitors. It works by reducing the effects of the 5α-reductase enzyme, which is responsible for the conversion of testosterone into DHT.
By blocking DHT production directly at the source, finasteride drastically reduces the amount of DHT that can bind to receptors in your scalp and other parts of your body. Research shows that finasteride can lower the amount of DHT in blood serum by as much as 70 percent.
Because of its effects on DHT, finasteride is highly effective at slowing down, stopping and even reversing hair loss from male pattern baldness.
In a study published in the Journal of the American Academy of Dermatology in the late 1990s, researchers found that men with pattern hair loss who used finasteride had clinically significant increases in hair count around the crown of the head.
A more recent study from Japan found that more than 91 percent of men who used finasteride to treat male pattern baldness experienced improvements in hair growth.
Although finasteride starts working right away, its effects on hair growth aren’t immediate. You may need to use finasteride for six to 12 months before you’ll be able to see improvements in your hair’s thickness, density and coverage.
We offer finasteride online, following a consultation with a licensed healthcare provider who will determine if a prescription is appropriate.
While finasteride works by blocking DHT at its source, other DHT blocking agents work locally by preventing it from damaging your hair follicles at the scalp level.
DHT blocking shampoos are widely available over the counter. They contain active ingredients that reduce the effects of DHT on your scalp and hair follicles, either by blocking DHT’s activity on the scalp or by washing away substances that contain DHT.
Over the years, several active ingredients have been identified as possibly stopping the effects of DHT, making them popular choices for DHT-blocking shampoos.
Look for the following ingredients when you’re comparing hair loss shampoos:
Ketoconazole. An antifungal medication, ketoconazole is commonly used to treat fungal skin infections such as athlete's foot (tinea pedis). It’s also known to inhibit 5α-reductase, the enzyme that converts testosterone into DHT.Research suggests that ketoconazole shampoo can increase hair density and stimulate hair follicles to enter the anagen phase of the hair growth cycle.
Saw palmetto. Saw palmetto is a popular natural ingredient that’s produced from a palm called Serenoa repens. A study published in the journal Urology found that it can reduce DHT levels in prostate tissue when taken as a supplement.Other research has found that saw palmetto can produce improvements in hair growth in men with pattern hair loss. You can find saw palmetto in our Hair Thickening Shampoo, which is formulated to target DHT and promote volume and moisture.
Pumpkin seed oil. Pumpkin seed oil is a natural product that’s been linked to improved hair growth. In one study, researchers found that it may stop prostate growth -- an issue that’s often caused by high DHT levels -- when used with saw palmetto. Other research suggests that pumpkin seed oil supplements can increase hair growth in men with male pattern baldness.
Although DHT blocking shampoos can produce improvements in hair growth, there’s much less scientific evidence to support their benefits than there is for finasteride.
In general, it’s best to use hair loss prevention shampoo with finasteride, rather than on its own as a hair loss treatment. Our guide to DHT blocking shampoos explains more about how a hair loss shampoo can fit into your hair care routine for optimal results.
Although DHT is the main hormone responsible for male pattern baldness, there’s more to hair loss prevention than just blocking it from affecting your hair follicles.
Other hair loss treatments may help to limit shedding and promote growth by moving hairs into the anagen phase of your hair growth cycle, improving blood circulation or providing your hairs with the nutrients they need to grow to their full strength, length and density.
In addition to the DHT blockers listed above, consider using the following treatments as part of your hair loss prevention routine:
Minoxidil is a topical medication for hair loss. It works by moving hairs into the anagen phase of the hair growth cycle and by increasing blood flow to the scalp.
Although minoxidil doesn’t lower DHT levels, it’s one of the most effective medications available for treating male pattern baldness, especially when it’s used in combination with finasteride.
In a study published in the journal Dermatologic Therapy, researchers found that 94.1 percent of men with androgenetic hair loss who used minoxidil and finasteride together saw improvements in their hair.
In comparison, 59 percent of men who used minoxidil alone and 80.5 percent of men who used finasteride also showed improvements.
Biotin, or vitamin B7, is a water-soluble that’s found in certain foods. It’s also a popular dietary supplement that serves as an important nutritional building block for thick hair, strong nails and healthy skin.
Research is mixed overall on the effectiveness of biotin as a hair growth supplement, although some studies of supplements containing biotin suggest that they may offer benefits.
DHT blockers are safe and effective for most men. However, some DHT-blocking medications may cause side effects, including sexual side effects.
These side effects only affect a small percentage of men who use finasteride. For example, data from clinical trials shows that erectile dysfunction -- the most publicized side effect of finasteride -- only occurred in 1.3 percent of men who used it at the standard 1mg dose.
Side effects from DHT blockers used in shampoos are uncommon. However, some ingredients used in hair loss prevention shampoos and other topical products may cause irritation, dry skin, itchy skin or other minor side effects.
If you experience any side effects while using finasteride or a topical DHT blocker, it’s important to let your healthcare provider know.
Hair loss from male pattern baldness can creep up on you, making it important to take action if you notice any of the early signs of balding.
Used effectively, DHT blockers like finasteride and our Hair Thickening Shampoo can help you to slow down or stop androgenic hair loss. In many cases, they can even stimulate growth and let you maintain a full head of thicker, healthier hair well into your 40s, 50s and 60s.
If you’ve noticed symptoms of DHT-related hair loss and want to take action, you can view our complete selection of hair loss treatments online.
You can also learn more about slowing down, stopping and reversing hair loss using finasteride in our full guide to finasteride for men.