Why Vitiligo Repigments in Dots: The Follicular Reservoir Explained

Ask anyone who has watched a vitiligo patch respond to treatment and they will describe the same thing: tiny brown dots appearing inside the white area, slowly widening until they merge. Clinicians call this perifollicular repigmentation, and it is the most common pattern seen with phototherapy, topical treatments, and newer JAK inhibitor creams. The dots are not a quirk. They are a direct readout of where the body keeps its backup supply of pigment cells.

The bulge: a protected melanocyte bank

In vitiligo, the immune system targets and eliminates melanocytes, the cells that make pigment, from the epidermis. But the skin holds a second population of pigment-producing cells in reserve. Deep in each hair follicle, in a region called the bulge, sit melanocyte stem cells. These cells are relatively shielded from the autoimmune attack for two reasons. First, the follicle is an immune-privileged site, meaning it actively suppresses local immune surveillance, partly through reduced expression of the molecules that flag cells for T cell attention. Second, melanocyte stem cells in their resting state produce little to no melanin and express low levels of the pigment-related proteins, such as tyrosinase and gp100, that cytotoxic T cells in vitiligo are trained to recognize. A cell that is not displaying the target antigen is much harder to find.

How the dots form

When treatment quiets the immune attack, whether through narrowband UVB, topical corticosteroids, calcineurin inhibitors, or topical ruxolitinib, the environment becomes safe enough for those stem cells to act. They divide, and their daughter cells migrate upward along the outer root sheath of the follicle, exit at the skin surface, spread laterally into the surrounding depigmented epidermis, and switch on melanin production. Because each follicle seeds its own small territory, pigment returns as a dot centered on a hair. UVB light appears to do double duty here: it dampens local immune activity and also directly stimulates melanocyte stem cell activation and migration, which is part of why phototherapy remains a backbone of vitiligo care.

Why lips, fingertips, and knuckles lag behind

This mechanism also explains one of the most frustrating realities in vitiligo treatment: response depends heavily on location. The face and neck, which are densely covered in fine vellus hairs and receive good blood supply, tend to repigment best. Hands, feet, lips, and bony prominences like knuckles and ankles respond poorly, and the follicular reservoir is a major reason. Lips and palmar skin have essentially no hair follicles, so there is no local stem cell bank to draw from. The backs of the hands have follicles, but they are sparse, and repeated friction and microtrauma in these areas may also sustain low-grade inflammation that keeps the immune attack simmering, a phenomenon related to the Koebner response, where new lesions appear at sites of skin injury.

Leukotrichia: when the reservoir itself is gone

Hair color offers a useful clinical clue. If the hairs within a vitiligo patch have turned white, a finding called leukotrichia, it usually means the autoimmune process has breached the follicle and destroyed the melanocyte stem cells too. Patches with extensive leukotrichia are far less likely to repigment with medical therapy alone, because the seed bank is empty. In stable disease, these areas are sometimes candidates for surgical approaches such as melanocyte-keratinocyte transplantation, which works by physically importing pigment cells from an unaffected donor site rather than waiting for local recovery that cannot happen.

Marginal repigmentation and what it signals

A second, less common pattern is marginal repigmentation, where color creeps inward from the edges of a patch. Here the pigment comes from healthy melanocytes at the border migrating sideways. This process is slow, typically advancing only a few millimeters, because mature epidermal melanocytes have limited migratory capacity compared with activated stem cells. Diffuse repigmentation, a general darkening across the whole patch without visible dots, is seen occasionally and may reflect surviving epidermal melanocytes that were suppressed rather than destroyed.

Practical takeaways

For patients and clinicians, the reservoir model translates into a few grounded expectations. Repigmentation is measured in months, not weeks, because stem cell activation, migration, and pigment spread are slow biological processes; most protocols assess response at three to six months before judging failure. Hairy sites are better candidates than glabrous sites, and treatment plans for lips or fingertips should be framed with modest expectations or steered toward surgical options once disease is stable. Pigmented hairs within a patch are a favorable sign worth noting at baseline. And the dotted, uneven look of early repigmentation is not a treatment gone wrong. It is the follicular reservoir doing exactly what it evolved to do, one follicle at a time.

Related reading: Why Repigmentation Starts as Tiny Dots Around Hair Follicles, and What That Tells You About Your Treatment.

Further reading: The immunology of vitiligo (Nat Rev Immunol 2026); Vitiligo (Ugeskr Laeger 2025); Comorbidities in Patients with Vitiligo: A Systematic Review and Meta-Analysis (J Invest Dermatol 2023).