Understanding the Science Behind Shampoo for Thinning Hair and Tips on Choosing the Right One

Whether we like it or not, a head full of thick, flowing locks is often promoted as the standard of beauty – but it’s not a reality for everyone. In fact, it’s estimated that 50% of women will experience hair loss or hair thinning in their lifetime, and it’s often completely out of their control. 

Luckily, the market is overflowing with hair care products claiming to combat hair thinning, but it can be hard to know where to begin or what will work. So, we spoke with three trichologists (licensed professionals who specialize in hair and scalp health) and asked them about all things hair thinning, the science behind shampoos for thinning hair, and how to make informed decisions about our hair care routines.

The difference between hair loss and hair thinning is fairly straightforward, says William Gaunitz, FWTS, certified trichologist and founder of Advanced Trichology. “Hair loss is when you are actively losing hair,” he says. “Thinning hair is when you have lost overall density because hair is not regrowing as usual. Hair loss can lead to thinning hair, but hair loss may also not become thinning hair if the hair loss stops.”

And there’s a variety of reasons why your hair may be thinning. From nutrient deficiencies to hormonal changes, external factors, and genetics, they can include:

• Nutrient deficiencies
• Hormonal changes
• External factors
• Genetics

If you’re experiencing hair thinning, trichologists recommend finding and addressing the underlying cause first or you may not see results. Gaunitz says that once you block the underlying cause, you should automatically see hair regrowth to some degree. “As a trichologist, it is my job to manage expectations as well as find the greatest potential with hair care products for my clients,” explains Gaunitz. “Many people have unreasonable expectations of what can be done related to hair regrowth. Typically, the best-case scenario with a proper thinning hair or hair regrowth protocol is to regrow what was lost in the last three to five years, depending upon the individual situation.”

In addition to maintaining a clean and healthy scalp, regularly washing your hair with shampoo specifically designed to combat hair thinning is key. Using hair-thinning shampoo will help remove build-up and balance the scalp to keep the hair healthy and in the growing phase. These products contain important ingredients that promote density and growth and help thicken existing strands, such as biotin, ketoconazole, caffeine, and minoxidil.

Biotin: This water-soluble vitamin is part of the vitamin B family, and improves the structure of keratin, a protein that makes up hair, skin, and nails. Biotin is known to boost hair health, including volume and coverage of the scalp. A study published in the Journal of Clinical and Aesthetic Dermatology found that women experiencing temporary hair thinning who took a supplement containing biotin over a six-month period had a significantly greater increase in thick hairs compared to a control group. If you want to add biotin to your hair care routine, you can take biotin as a supplement to encourage hair growth or look for a shampoo that includes it as an ingredient. 

Ketoconazole: Ketoconazole treats infections caused by fungus or yeast, as well as conditions like dandruff and seborrheic dermatitis (scaly patches on the scalp) by lowering levels of yeast and inflammation. Tabitha Fredrichs, a certified trichologist and educator says that ketoconazole is an antifungal, and unless you are having hair loss from scalp fungus, this will not help with hair thinning. This ingredient comes in over-the-counter products or prescription medicated shampoos that block the enzyme 5-AR in your body. This enzyme lowers testosterone levels to promote hair growth. While the research is limited, some data suggests that ketoconazole can effectively stimulate hair growth.

Caffeine: While an extra shot of espresso in your morning latte can get you moving for the day, caffeine can also provide other boosts. The stimulant is known to increase circulation, which allows beneficial nutrients and oxygen to be delivered to the hair follicles to keep them healthy and growing. Research has shown that caffeine can help block the conversion of testosterone to dihydrotestosterone (DHT), a hormone that has been linked to hair follicle damage, which can lead to androgenetic alopecia, also known as female-pattern hair loss. 

Minoxidil: If you suffer from alopecia or severe hair thinning, a dermatologist might prescribe minoxidil. Fredrichs says the solution is not used in shampoos, but is an active ingredient in products like Rogaine and is applied directly to the scalp. The drug works to increase the size of hair follicles which promotes thicker hair. It’s only one of two FDA-approved treatments to regrow hair, following various studies looking into its effectiveness. 

Some hair-thinning shampoos even have ingredients like saw palmetto to help slow down genetic hair loss, or tea tree oil and rosemary oil which work as antiseptics that decrease fungus on the scalp.

While you might think lathering up with a shampoo or mask twice a week will fix the problem, it’s important to note that no over-the-counter product can reverse or cure hair thinning. Volumizing agents and scalp treatments with certain ingredients (like those mentioned earlier) can help the problem and provide some relief. But if you’ve noticed a loss of density in your hair or persistent hair thinning, you should speak with a licensed professional to formulate the best-personalized treatment plan. 

Kayla Jones, certified trichologist and owner of HairJones411 Hair Clinic says she creates a regimen that structures the client's diet, exercise, hair styling, treatment schedule, and vitamin intake. “Most clients neglect self-care and, crazy enough, stress is one of the major causes of hair loss,” she says. “I recommend products to each client to help control their progress throughout their hair restoration journey.”

Each person’s scalp is unique, so what might work for one person won’t work for another. Factors like scalp health and the cause and severity of hair thinning are all things to consider when choosing the right hair-thinning shampoo. And Jones recommends looking for products free of harsh chemicals, sulfates, and parabens, which can further damage fragile hair.

“It is very important,” explains Jones. “Parabens are known for interfering with hormones in the body.  When your hormones are imbalanced, you lose your hair. Sulfates strip the hair of dirt and natural oils and can also irritate the scalp. If you decide to use products with sulfates, I recommend using them one to two times per month.”

While OTC and prescription shampoos can be helpful, there are numerous complementary practices that can help support hair health. These include:

Gaunitz adds that things like excessive alcohol, smoking cigarettes, vaping, medication, and recreational drugs may have a negative liver and kidney burden. “If those organs are overworked, it [can] have a negative consequence on your hair and immune system,” he says.

If you notice hair thinning or loss of hair density, it’s important to equip yourself with the best evidence-based information when considering shampoos for thinning hair. Adopting a holistic approach to hair care that combines the use of appropriate shampoos with other healthy habits is a great place to start, but don’t hesitate to seek professional advice if you’re not seeing results. With the proper support and knowledge, you can embrace a future where healthy, full hair is a reality.