If you’ve spent any time reading about hair loss treatments, you will have come across DHT blockers. These are one of the most popular treatments for androgenetic alopecia (pattern hair loss). This is because DHT is the primary hormonal driver behind follicle miniaturisation in both men and women who are genetically susceptible to pattern hair loss. As such, blocking DHT can be one of the most effective ways to slow, halt and in many cases reverse androgenetic hair loss. However, the term “DHT blocker” loosely covers several different types of medication that work through quite distinct mechanisms. There are also quite serious possible side effects with using these hormone blocking treatments. In this article, we explore what DHT blockers are, how they work and who they are suitable for. We’ll also compare different DHT blockers for effectiveness, safety and side effects.
What is DHT & Why Does it Cause Hair Loss?
Before understanding how DHT blockers work, it helps to understand how DHT causes hair loss. Dihydrotestosterone (DHT) is an androgen hormone that is produced when testosterone is converted by an enzyme called 5-alpha reductase. DHT is present in both men and women and plays important roles in the body, particularly during puberty. However, in people who are genetically predisposed to pattern hair loss, DHT binding to androgen receptors on scalp hair follicles can trigger a process called follicular miniaturisation. Over time, the affected follicles shrink, producing increasingly thinner and shorter hairs. Without intervention, they eventually stop producing visible hairs altogether.
This process typically follows a specific pattern. In men, it usually begins with recession at the temples and thinning at the crown, progressing through the stages of the Norwood Scale. In women, it tends to present as diffuse thinning across the top of the scalp but there is little to no effect on the frontal hairline. Reducing DHT levels or blocking its action on the follicle can halt this hair loss by stopping miniaturisation.
How Do DHT Blockers Work?
It’s worth thinking of the term “DHT blocker” as an umbrella that covers two fundamentally different mechanisms. The first which most people associate with the term are direct DHT blockers. It is also possible to indirectly block DHT which can also be effective but fewer people know about. The main ways to block DHT are:
- 5-Alpha Reductase Inhibitors: These work by directly blocking the enzyme that converts testosterone into DHT in the first place. By inhibiting this conversion, they reduce the amount of DHT available to damage hair follicles. The two main drugs in this category are finasteride and dutasteride. These are the most potent and well-studied DHT blockers available and are the treatments most people are referring to when they talk about “DHT blockers” for hair loss.
- Androgen Receptor Blockers: These are not DHT blockers in the pure sense but they offer a similar outcome. Rather than reducing the amount of DHT produced, these agents block the androgen receptors on the hair follicle. This means that DHT cannot bind to them and exert its miniaturising effect. Spironolactone is the main example of an indirect DHT blocker.
What are the Different Types of Prescription DHT Blockers?
There are three main prescription DHT blockers which have uses in treating hair loss. They work by either blocking the enzyme that converts testosterone into DHT or by blocking androgen receptors so that DHT cannot bind to hair follicles in the first place. The main prescription medicines used to block DHT in androgenetic hair loss are:
- Finasteride: This is the most widely prescribed DHT blocker. It selectively inhibits the type II 5-alpha reductase enzyme, reducing scalp DHT by approximately 70%. Finasteride has over 25 years of clinical evidence and is licensed for use in men with hair loss as a 1mg daily oral medication in the UK under the brand name Propecia. It is also becoming increasingly popular in topical compounded formulations for men and post-menopausal women. The aim of these is to deliver DHT-blocking activity locally whilst reducing systemic absorption. The main concern with Finasteride is its side effect profile. Risks include sexual dysfunction, mood disturbances and in some cases depression and suicidal ideation. There is also the issue of Post-Finasteride Syndrome where side effects persist after discontinuation. Even topical finasteride cannot entirely eliminate these systemic risks.
- Dutasteride: This is the more potent option alternative to Finasteride. It inhibits both the type I and type II 5-alpha reductase isoenzymes (finasteride blocks only type II). This gives it a broader suppression of DHT production, reducing serum levels by up to 90%. Dutasteride is not licensed for hair loss in any form. However it is sometimes prescribed off-label as a second-line option for men or post-menopausal women who have not responded adequately to finasteride. Its side effect profile is similar to finasteride but potentially more pronounced due to its greater potency. It also has a much longer half-life (approximately 5 weeks vs 6 to 8 hours for finasteride) which means side effects may take longer to resolve after stopping the drug.
- Spironolactone: This blood pressure medication blocks androgen receptors on the hair follicle and also reduces overall androgen production. As such it is sometimes used off-label/license orally or topically to treat pre and post-menopausal women with androgenetic hair loss. In men, oral spironolactone can cause feminising side effects such as breast enlargement, decreased libido and erectile dysfunction. For this reason, the topical form is usually only used for men.
Oral vs Topical DHT Blockers
One of the most important decisions when considering DHT blockers is whether to use the oral or topical form. Topical treatments are becoming more popular due to possibly lower risk of side effects whilst oral medicines provide the most convenience. As always the best solution differs from person to person.
- Oral DHT blockers: These normally come in tablet form which your body absorbs and delivers through the blood stream. This means they reduce DHT levels throughout the entire body, not just at the scalp. The advantage is you get consistent dosing and reliable absorption. The disadvantage is that there’s a higher risk of systemic side effects because the drug affects DHT everywhere including the brain, prostate and reproductive system.
- Topical DHT blockers: These come in serum, spray or foam formulas. You apply them directly to the scalp, aiming to deliver the active ingredient locally to the hair follicles whilst limiting how much enters the bloodstream. The advantage is they act directly at the site of hair loss and reduce systemic side effects as there’s less absorption into the blood stream. However, some systemic absorption still occurs with topical use and so there is still a chance of side effects.
Can You Combine DHT Blockers with Other Hair Loss Treatments?
DHT blockers address the hormonal cause of pattern hair loss but they are usually more effective when combined with treatments that stimulate hair growth through different pathways. The most common ingredients to combine with DHT blockers include:
- Minoxidil: This is the gold standard combination for pattern hair loss. Minoxidil promotes hair growth by improving blood flow to the follicle and prolonging the anagen phase independently of the androgen pathway. Using it alongside a DHT blocker means you are both protecting follicles from further damage and actively stimulating new growth. Research consistently shows that this combination produces better outcomes than either treatment alone.
- Tretinoin: Topical tretinoin can enhance the absorption and effectiveness of topical minoxidil and DHT blockers. It may also support hair follicle health through its effects on skin cell turnover.
- Supportive adjuncts: Ingredients like melatonin, caffeine and microneedling can all complement the actions of DHT blockers and minoxidil. Low-level laser therapy (LLLT) is another adjunct that can support hair follicle activity.
What About Over-the-Counter & Natural DHT Blockers?
In addition to prescription medications, there are a number of over-the-counter products and natural ingredients that claim to reduce DHT or block its effects on hair follicles. These are considerably less potent than prescription DHT blockers and the evidence supporting them is generally weaker. However, they may play a supportive role alongside proven treatments:
- Ketoconazole: This is an antifungal medication available in medicated shampoos (such as Nizoral) that has shown some anti-androgen activity. It can help by reducing local DHT levels on the scalp and addressing scalp inflammation which can contribute to hair loss.
- Saw Palmetto: This plant extract is thought to inhibit 5-alpha reductase in a similar way to finasteride albeit at a much lower level. Some small studies have shown modest improvements in hair density with saw palmetto supplementation but the evidence is inconclusive.
- Pumpkin Seed Oil: A small randomised trial showed improvements in hair count in men who used pumpkin seed oil over 24 weeks. However, data is still very scarce in terms of true effectiveness, optimal use, comparison with DHT blockers and safety.
It’s important to manage expectations with natural DHT blockers. They are unlikely to produce results comparable to finasteride, dutasteride or spironolactone. However, for people with very early or mild thinning or for those who cannot or do not wish to use prescription medications, they may offer modest benefit as part of a broader hair care routine.
DHT blockers are the most effective class of treatment for addressing the hormonal cause of androgenetic alopecia. Whilst they can be very effective, DHT blockers carry meaningful side effects. These need careful weighing against their benefits. For many patients, topical formulations can potentially minimise these risks but they do not eliminate them. Additionally, they are much more effective in combination with treatments that stimulate growth. Lastly, whilst there are some “natural DHT blockers”, there’s not much information regarding their safety, effectiveness or how they compare to formal medications. They may however be useful as a supportive treatment or for those not wanting to use prescription treatments,
At City Skin Clinic, we provide custom topical hair loss treatments for women and men in the UK. This allows our doctors to deliver DHT-blocking ingredients directly to the scalp as part of compounded treatments. Our doctors create custom hair growth treatments using actives such as Minoxidil, Finasteride, Dutasteride, Spironolactone, Melatonin, Caffeine and Tretinoin where appropriate. Start your virtual consultation and begin your journey to great hair today.
This article is intended for general informational purposes only and is not a substitute for medical advice, diagnosis or treatment. Always consult a qualified medical professional with any concerns about your hair or treatment options.
