Hair Aging Revisited: An Expert Delphi Consensus on Pathogenesis, Clinical Features, and Future Therapies

Hair follicle (HF) aging is a complex process involving gradual deterioration in the function and structure of the HF, adding to degenerative changes in the hair shaft caused by weathering. Despite growing research interest, hair aging remains inconsistently defined in clinical practice, with no universally accepted classification or management guidelines. This study aimed to define hair aging and achieve consensus on diagnostic and management of hair aging. A modified Delphi methodology was used. A European and USA-based scientific committee developed a structured questionnaire, which was distributed to a panel of 24 dermatologists in Europe. Each statement was rated on a 9-point Likert scale. Consensus was defined as a median score of 1–3 or 7–9 with < 1/3 of responses outside this range and an interquartile range (IQR) < 4. Of the 65 statements, 51 (78.5%) reached consensus. Experts agreed that hair aging includes both quantitative and qualitative changes involving pigment loss, hair follicle miniaturization, and declining hair fiber quality. Hair graying was attributed to oxidative stress, melanocyte depletion, and diminished pigmentation-related signaling. Several contributing risk factors were identified. Senescent alopecia was defined as diffuse hair thinning in both androgen-dependent and -nondependent areas. Although diagnostic overlap with androgenetic alopecia (AGA) was acknowledged, the panel emphasized distinct underlying pathophysiology for hair aging, with stem cell exhaustion, fibrosis, and immunosenescence as suspected key mechanisms. Preventative care through lifestyle modification and supportive hair care practices was widely endorsed. Minoxidil was the only pharmacologic therapy to receive consensus support, while other emerging therapies to slow HF aging require further investigation. This Delphi consensus provides a structured expert overview of hair aging, highlights areas of agreement and uncertainty, may assist in improving diagnostic accuracy and more consistent management strategies for age-related hair changes, and identifies potential new targets for therapeutic intervention. Graphical Abstract available for this article. Hair aging is a natural process where hair follicles (the skin structure where hair grows) lose function over time. This leads to graying, thinning, fragility, and sometimes hair loss. Although normal with age, early or severe changes can affect self-esteem and quality of life. This study was carried out in Europe by dermatologists from several countries. Experts in hair disorders aimed to describe what happens during the hair aging process, identify the main factors that can lead to premature hair aging, and offer practical recommendations for prevention and management. These conclusions are based on current scientific evidence and expert opinion. Five experts reviewed scientific studies about hair aging and then wrote 65 statements about hair aging. These statements were sent to 24 dermatologists across Europe. The dermatologists voted on the different statements over two rounds of voting to reach agreement (consensus). Experts agreed that hair aging involves both graying and structural changes in the follicle and hair shaft. Genetics, lifestyle, and environmental factors influence its severity. Signs may be partly reversible, and minoxidil may help in some cases. Cosmetic products can improve appearance, but effective therapies to reverse graying are not yet available. The study provides the first expert-based definition and guidance on hair aging. It highlights that hair aging is not just cosmetic but can affect well-being. Clearer definitions will help doctors counsel patients, guide treatment choices, and support future research into therapies.