Trichoscopy

Trichoscopy is the dermoscopic examination of the scalp and hair, performed with the same handheld dermatoscope used for skin lesions but applied to the hair-bearing scalp, eyebrows, and beard. By providing magnified, polarized-light visualization of the hair shafts, follicular openings, and perifollicular skin, trichoscopy supports the recognition of patterns that distinguish one hair disorder from another and enables earlier, more accurate diagnosis of hair loss conditions.

How Trichoscopy Works

Trichoscopy uses a handheld dermatoscope, with or without contact and immersion fluid, to magnify the scalp surface up to approximately ten times. Polarized light eliminates surface reflection and reveals features that lie below the cuticle and within the follicular ostia. The clinician evaluates hair shaft diameter and uniformity, the presence of broken or tapered hairs, the colour and pattern of follicular openings, perifollicular scaling or pigmentation, and the configuration of scalp vessels.

These observations are then matched against established diagnostic criteria for individual hair and scalp disorders. A characteristic pattern of yellow dots, black dots, exclamation-mark hairs, and short broken hairs, for example, supports a diagnosis of alopecia areata, while the loss of follicular ostia, perifollicular erythema, and follicular hyperkeratosis suggests a scarring alopecia.

Clinical Applications

Trichoscopy is used to evaluate the broad range of hair and scalp conditions seen in dermatology practice. In non-scarring alopecias, it helps differentiate alopecia areata, androgenetic alopecia, telogen effluvium, and trichotillomania, each of which has a distinct trichoscopic signature. In scarring alopecias such as frontal fibrosing alopecia, lichen planopilaris, and central centrifugal cicatricial alopecia, trichoscopy identifies the loss of follicular openings and perifollicular changes that define this group of conditions.

Beyond hair loss, trichoscopy contributes to the assessment of inflammatory scalp diseases such as scalp psoriasis and seborrhoeic dermatitis, where vascular patterns and scaling characteristics differ in informative ways. It also supports the diagnosis of tinea capitis through the recognition of comma hairs, corkscrew hairs, and zigzag hairs, and assists in the evaluation of trichotillomania, where broken hairs of varying lengths and characteristic shaft abnormalities are typically present.

Common Trichoscopic Findings

A number of trichoscopic features have well-defined diagnostic associations. Yellow dots, which represent dilated follicular ostia filled with sebum and keratin, are a hallmark of alopecia areata and androgenetic alopecia. Exclamation-mark hairs, characterized by tapered proximal ends, are highly suggestive of active alopecia areata. Hair shaft diameter variability greater than twenty percent within a defined area is a key marker of androgenetic alopecia.

In scarring alopecias, the loss of follicular ostia is the cardinal finding and is often accompanied by perifollicular erythema, white dots, and follicular hyperkeratosis. In trichotillomania, broken hairs of varying lengths, flame hairs, and tulip hairs are commonly observed. Recognition of these features allows the clinician to direct subsequent investigations, such as scalp biopsy, only when truly needed.

Quantitative Trichoscopy and Androgenetic Alopecia

Beyond pattern recognition, contemporary trichoscopy increasingly relies on quantitative image analysis to generate objective, reproducible measurements of scalp and hair parameters. Standardized images captured from defined scalp regions can be processed by computer-assisted software to derive hair count, hair density per square centimetre, mean hair shaft diameter, the proportion of vellus and intermediate hairs, and the distribution of single, double, and triple follicular units. These parameters, taken together, provide a numerical fingerprint of the scalp that complements visual pattern recognition.

Quantitative trichoscopy is particularly valuable in the assessment of androgenetic alopecia, where the diagnosis rests on a constellation of measurable changes rather than on a single distinctive feature. The hallmark abnormality is anisotrichosis, defined as a hair shaft diameter variability of greater than approximately twenty percent within an androgen-dependent scalp region. This finding is reliably detected only when shaft diameters are measured rather than estimated by eye. Additional quantitative markers include a reduced overall hair density, an increased ratio of vellus to terminal hairs, and a shift toward single-hair follicular units in the affected zones.

Comparing measurements from the affected vertex, frontal, or mid-scalp areas with measurements from the occipital scalp, which is generally spared in androgenetic alopecia, allows early-stage disease to be recognized before substantial visible thinning has developed. Serial quantitative trichoscopy at follow-up visits then provides an objective measure of response to medical therapy, capturing changes in density, shaft diameter, and vellus-to-terminal ratios that may be too subtle for global photography or patient self-assessment to detect reliably.

The Examination Process

A trichoscopic examination is performed during the medical dermatology consultation and requires no special preparation. Hair does not need to be washed, shaved, or styled in any particular way before the appointment. The dermatoscope is gently placed against several representative areas of the scalp, and additional sites are examined when localized abnormalities are identified.

The procedure is painless and typically takes only a few minutes. When quantitative analysis is indicated, standardized images of predefined scalp areas are captured for image processing, with care taken to maintain consistent positioning, magnification, and lighting so that follow-up measurements remain directly comparable. Findings are correlated with the clinical history, the hair pull test where appropriate, and any laboratory investigations indicated by the suspected diagnosis.

Trichoscopy in Diagnosis and Treatment Monitoring

Serial trichoscopy is particularly useful for monitoring response to treatment in alopecia areata, androgenetic alopecia, and the scarring alopecias. The reappearance of regrowing pigmented hairs, the resolution of exclamation-mark hairs, or the stabilization of perifollicular inflammation provides objective evidence of response that complements patient-reported outcomes. In scarring alopecia, where prompt control of inflammation is essential to limit permanent follicular loss, trichoscopy supports earlier intervention and more responsive adjustment of therapy, including the use of biologic and advanced small molecule therapy when indicated.

Together with dermoscopy of the skin, trichoscopy and its quantitative extensions form part of the routine diagnostic toolkit at the Centre for Medical and Surgical Dermatology. Dr. Maksym Breslavets incorporates trichoscopic evaluation, supplemented by computer-assisted image analysis when appropriate, into the assessment of patients presenting with hair loss, scalp inflammation, and other hair-related concerns, ensuring that diagnostic and treatment decisions are guided by the most informative non-invasive information available.