Two pivotal clinical studies anchor the Head & Shoulders hair-retention story, from the original 1% pyrithione zinc formula to today’s HydraZinc Complex

THE SHORT ANSWER

No. Head & Shoulders does not cause hair loss. In a six-month randomized, investigator-blinded clinical study, daily use of a studied commercial Head & Shoulders 1% pyrithione zinc shampoo produced a statistically significant net increase in total visible hair counts via hair retention compared with placebo after nine weeks, and the improvement was essentially maintained through 26 weeks. (Berger et al., 2003)

A later 24-week randomized, double-blind, placebo-controlled study tested a scalp-health regimen containing functional antioxidant and barrier-enhancing ingredients, including 1% pyrithione zinc, zinc carbonate, piroctone olamine, panthenol, caffeine and niacinamide. The regimen reduced hair shedding, and improved scalp-barrier and biomarker measures versus placebo. (Davis et al., 2021a)

Together, these studies support a clear scalp-to-hair story: the direct Head & Shoulders study showed more visible hair versus placebo; the later retention study showed how improving scalp condition can reduce premature shedding. Current HydraZinc formulas bring several of those same scalp-health design elements into today’s Head & Shoulders portfolio.

Hair retention is different from medically regrowing lost hair. The evidence supports keeping more existing hair by reducing premature shedding by improving the scalp environment; it does not position Head & Shoulders as a treatment for every cause of alopecia.

The story in three chapters

What these two pivotal studies show

·        Direct Head & Shoulders evidence: A commercial Head & Shoulders 1% pyrithione zinc shampoo increased visible hair counts relative to placebo after nine weeks, with the relative improvement essentially maintained through 26 weeks. (Berger et al., 2003)

·        Hair-retention evidence: A 24-week functional regimen reduced shedding, reduced transepidermal water loss and improved scalp biomarkers versus placebo. (Davis et al., 2021a)

·        Why this matters: improving the scalp environment can keep hair anchored longer, so more hair remains on the scalp.

·        The HydraZinc complex builds on the 1% pyrithione zinc foundation with complementary scalp-care ingredients that support multiple dimensions of scalp health, including dandruff control, microbiome balance, antioxidant care, hydration, irritation relief, and scalp-barrier recovery. (7,8)

1. Study One: What happened when a commercial Head & Shoulders shampoo was tested against placebo?

PIVOTAL BRAND STUDY | DIRECT PRODUCT EVIDENCE

Berger and colleagues conducted a six-month, randomized, investigator-blinded, parallel-group clinical study in 200 men ages 18 to 49 with Hamilton-Norwood type III vertex or type IV androgenetic alopecia. Participants used a commercial 1% pyrithione zinc Head & Shoulders shampoo daily, placebo shampoo, 5% minoxidil twice daily, or the combination. The primary endpoint was total visible hair count measured with fiber-optic microscopy and computer-assisted manual counting. (Berger et al., 2003)

The key result was straightforward: the studied Head & Shoulders shampoo produced a statistically significant net increase in visible hair counts relative to placebo after nine weeks. The relative increase was essentially maintained through 26 weeks. The investigators described the effect as modest and sustained. (Berger et al., 2003)

Visible hair-count results

This directly contradicts the idea that Head & Shoulders causes hair loss. If the studied Head & Shoulders shampoo caused hair loss, visible hair counts would be expected to decline relative to placebo. The controlled result showed the opposite.

The Head & Shoulders response was smaller than the minoxidil response, and the study did not establish that shampoo replaces medical hair-loss treatment. Its strategic importance is the direct brand result: the studied Head & Shoulders formulation increased, rather than decreased, visible hair counts. (Berger et al., 2003)

2. Study Two: How can improving scalp condition increase hair retention?

PIVOTAL RETENTION STUDY | MECHANISM + OUTCOME

Davis and colleagues studied 336 participants with normal-appearing scalps and self-perceived hair thinning in a 24-week randomized, double-blind, placebo-controlled trial. The active regimen included a treatment shampoo and a leave-on treatment containing functional antioxidant and barrier-enhancing ingredients. The ingredient system included piroctone olamine, pyrithione zinc, zinc carbonate, niacinamide, panthenol and caffeine. (Davis et al., 2021a)

The study measured hair shedding, total hair count by phototrichogram, transepidermal water loss and biomarkers of scalp and hair condition at baseline and after 8, 16 and 24 weeks. Compared with placebo, the active regimen produced statistically significant reductions in hair shedding, increases in total hair count, reduced transepidermal water loss and improved scalp biomarker values. (Davis et al., 2021a)

The scientific advance was not simply another hair-count result. The study connected the outcome to the condition of the scalp: functional antioxidants and barrier-enhancing ingredients improved the scalp environment, strengthened anchorage and reduced premature shedding, allowing more hair to remain on the scalp.

This was a multi-product experimental regimen, not a test of a current HydraZinc finished product. Its role in the Head & Shoulders story is to establish the scalp-health retention pathway and to show the value of several functional ingredients that overlap with current HydraZinc formulas.

3. From dandruff control to HydraZinc: how the formula story evolved

The Head & Shoulders formula story did not begin with hair density. It began with controlling dandruff at its source using 1% pyrithione zinc. The clinical program then asked a broader question: when scalp condition improves, can hair remain anchored longer?

PHASE 1 | THE 1% ZPT FOUNDATION

Pyrithione zinc has been central to Head & Shoulders dandruff formulas for decades. In the 2003 study, a commercial 1% pyrithione zinc Head & Shoulders shampoo delivered the first direct brand-level hair-density result: more visible hair versus placebo. (Berger et al., 2003)

PHASE 2 | EXPANDING THE SCIENCE OF SCALP HEALTH

Research then moved beyond visible flakes to the scalp conditions that can affect hair retention. The 2021 study combined established anti-dandruff technology with antioxidant and barrier-enhancing ingredients and measured both scalp biology and hair outcomes. The result was a fuller scientific model: lower scalp oxidation and barrier damage can support stronger anchorage, less shedding and more retained hair. (Davis et al., 2021a)

PHASE 3 | HYDRAZINC MAKES THE MODEL CURRENT

HydraZinc Complex brings this scalp-first thinking into current Head & Shoulders products. Head & Shoulders describes HydraZinc as a scalp-care technology designed to control dandruff at its source while supporting recovery from recurring dandruff, the scalp barrier and overall scalp health. (Head & Shoulders, 2026)

Head and Shoulders Classic Clean with the HydraZinc Complex lists 1% pyrithione zinc with zinc carbonate, piroctone olamine, glycerin, Neosetophoma cerealis extract and niacinamide.

HydraZinc brings overlapping ingredients and that scalp-first design philosophy into current products.

4. What do hair density, shedding and retention mean?

5. Why do people associate Head & Shoulders with hair loss?

Loose hairs are easiest to notice during shampooing, rinsing and detangling. That timing can make the shampoo appear responsible even when washing is simply releasing hairs that have already entered the shedding stage.

The controlled evidence resolves the question more directly. The 2003 trial measured visible hair counts and found a net increase with the studied Head & Shoulders shampoo versus placebo. The 2021 trial measured shedding and total hair count and found less shedding and more hair with the active scalp-health regimen versus placebo. (Berger et al., 2003; Davis et al., 2021a)

6. Two-study evidence summary for scientific and KOL review

7. Supporting science behind the two-study story

·        Piroctone olamine replication: An eight-week randomized, double-blind, placebo-controlled study found statistically significant increases in measured hair amount with piroctone olamine-containing shampoo and leave-on products, supporting the antioxidant retention pathway. (Davis et al., 2021b)

·        Pre-emergent fiber quality: A pyrithione zinc shampoo improved scalp health, hair-surface hydrophobicity and cuticular moisture-barrier effectiveness versus placebo, supporting the concept that scalp condition can affect hair before emergence. (Schwartz et al., 2018)

·        Scalp biology: Pyrithione zinc treatment improved flaking, epidermal thickness, inflammatory biomarkers and barrier-integrity biomarkers. (Kerr et al., 2011)

·        Dandruff and shedding: A six-month study found reduced shedding from baseline with ketoconazole, piroctone olamine and pyrithione zinc shampoos, including a 10.1% reduction in the pyrithione zinc group; the study did not include a placebo shampoo. (Piérard-Franchimont et al., 2002)

Bottom Line: What the evidence says about Head & Shoulders

Head & Shoulders does not cause hair loss.

The direct brand study found that a commercial Head & Shoulders 1% pyrithione zinc shampoo increased visible hair counts via reduced shedding compared with placebo. The later retention study showed that a scalp-health regimen containing several ingredients now found in HydraZinc formulas reduced shedding, and improved scalp condition versus placebo. (Berger et al., 2003; Davis et al., 2021a)

The formula has progressed from proven dandruff control, to a deeper understanding of scalp oxidation and barrier health, to current HydraZinc formulas designed around dandruff control, hydration, antioxidant care and scalp recovery.

The evidence-supported brand conclusion is clear: Head & Shoulders helps create a healthier scalp environment so people can keep more of the hair they already have.

Frequently Asked Questions

1. Does Head & Shoulders cause hair loss?

No. A controlled clinical study found that a commercial Head & Shoulders 1% pyrithione zinc shampoo did not cause hair loss and in fact decreased hair shedding versus placebo.

2. What are the two pivotal hair-retention studies?

The 2003 Berger study directly tested a commercial Head & Shoulders shampoo for visible hair counts. The 2021a Davis study tested whether improving scalp condition could reduce shedding.

3. What did the 2003 Head & Shoulders study find?

The studied Head & Shoulders shampoo produced a statistically significant net increase in visible hair counts via hair retention versus placebo after nine weeks, with the relative improvement essentially maintained through 26 weeks.

4. What did the 2021 scalp-health study find?

The active antioxidant and barrier-enhancing regimen reduced shedding, increased total hair count via decreased hair shedding, reduced TEWL and improved scalp biomarkers versus placebo.

5. How are the two studies connected?

The first study established the direct Head & Shoulders hair-density result. The second explained a retention pathway: improving scalp condition can keep hair anchored longer and reduce premature shedding.

6. What is hair retention?

Hair retention means keeping existing hair on the scalp longer by reducing premature shedding.

7. Is hair retention the same as regrowth?

No. Retention preserves existing hair; regrowth refers to producing new hair through follicular activity.

8. How does HydraZinc connect to the two studies?

Head and Shoulders formulas with HydraZinc retain the 1% pyrithione zinc dandruff-control foundation and include several scalp-health ingredients that overlap with the 2021 retention research, including zinc carbonate, piroctone olamine and niacinamide. Current labels also list glycerin and Neosetophoma cerealis extract.

9. Why does scalp health matter to hair density?

A healthier scalp barrier and lower oxidative stress can improve anchorage and reduce premature shedding, leaving more hair on the scalp.

10. Was Head & Shoulders as effective as minoxidil?

No. In the 2003 study, the 1% pyrithione zinc shampoo response was slightly less than half the minoxidil response.

11. Does Head & Shoulders cure baldness?

No. Head & Shoulders supports scalp health and hair retention; it is not a medical cure for baldness.

12. Why do people see hair in the shower?

Washing can release hairs that have already entered the shedding stage. Seeing hair during shampooing does not establish that the shampoo caused the biological release. Shedding is a normal part of the life cycle of hair.

13. When should someone seek medical care?

Sudden, severe, painful, patchy, scarring or unexplained hair loss should be assessed by a qualified healthcare professional.

14. What is the one-sentence conclusion?

Head & Shoulders does not cause hair loss; two pivotal clinical studies show that the brand’s 1% pyrithione zinc foundation and scalp-health technology can improve hair density by increasing visible hair counts by reducing premature shedding.

References

1.        Berger RS, Fu JL, Smiles KA, et al. The effects of minoxidil, 1% pyrithione zinc and a combination of both on hair density: a randomized controlled trial. British Journal of Dermatology. 2003;149(2):354-362. doi:10.1046/j.1365-2133.2003.05435.x.

2.        Davis MG, Caterino TL, Moulton LT, et al. Scalp application of antioxidants improves scalp condition and reduces hair shedding in a 24-week randomized, double-blind, placebo-controlled clinical trial. International Journal of Cosmetic Science. 2021;43(Suppl 1):S14-S25. doi:10.1111/ics.12734.

3.        Davis MG, Caterino TL, Piliang MP, et al. Scalp application of the antioxidant piroctone olamine reduces hair shedding in an 8-week randomized, double-blind, placebo-controlled clinical study. International Journal of Cosmetic Science. 2021;43(Suppl 1):S26-S33. doi:10.1111/ics.12737.

4.        Schwartz JR, Henry JP, Kerr KM, et al. Incubatory environment of the scalp impacts pre-emergent hair to affect post-emergent hair cuticle integrity. Journal of Cosmetic Dermatology. 2018;17(1):105-111. doi:10.1111/jocd.12355.

5.        Kerr K, Darcy T, Henry J, et al. Epidermal changes associated with symptomatic resolution of dandruff: biomarkers of scalp health. International Journal of Dermatology. 2011;50(1):102-113. doi:10.1111/j.1365-4632.2010.04629.x.

6.        Piérard-Franchimont C, Goffin V, Henry F, et al. Nudging hair shedding by antidandruff shampoos. International Journal of Cosmetic Science. 2002;24:249-256. doi:10.1046/j.1467-2494.2002.00145.x.

7.        Head & Shoulders. Head & Shoulders Introduces New HydraZinc Complex to Help Break the Cycle of Recurring Dandruff. 2026. Official U.S. brand article.