Peripilar sign, yellow dots, and vellus hair predominance are the three most clinically significant trichoscopy findings in androgenetic alopecia (AGA), and each one has a measurable counterpart in AI-powered home density tracking. This guide maps specific dermoscopic findings to the metrics you can monitor with myhairline.ai, connecting clinical microscopy to your everyday tracking data.
This content is for informational purposes only and does not constitute medical advice. Consult a dermatologist for personalized diagnosis and treatment.
Trichoscopy Fundamentals
Trichoscopy is the dermoscopic examination of the scalp and hair using a handheld dermatoscope (typically at 10-70x magnification). It allows dermatologists to visualize structures invisible to the naked eye: individual follicular openings, hair shaft thickness variations, perifollicular inflammation, and scalp surface patterns.
In a clinical setting, trichoscopy takes 5-15 minutes and provides immediate visual information that guides diagnosis. For androgenetic alopecia specifically, trichoscopy identifies patterns that distinguish AGA from other conditions like alopecia areata, telogen effluvium, or scarring alopecia.
The findings fall into several categories, each carrying diagnostic significance:
| Trichoscopy Finding | Appearance | What It Indicates |
|---|---|---|
| Peripilar sign | Brown halo around follicle opening | Perifollicular inflammation and fibrosis |
| Yellow dots | Yellow/amber dots at follicle sites | Empty or miniaturized follicles filled with sebum |
| Vellus hair predominance | Thin, light, short hairs outnumbering thick hairs | Active follicle miniaturization |
| Hair diameter diversity | Mixed thick and thin hairs in same area | Early to mid-stage AGA progression |
| White dots | Small white spots in scalp | Fibrotic or scarred follicles (late stage) |
| Honeycomb pattern | Regular pigmented scalp network | Normal scalp (baseline reference) |
The Peripilar Sign and Density Decline
The peripilar sign appears as a dark brown halo surrounding the follicular opening. It indicates perifollicular inflammation and early fibrosis, both of which precede visible hair thinning. In clinical studies, the peripilar sign is found in up to 65% of AGA patients and is considered one of the earliest detectable markers.
What AI Tracking Sees Instead
myhairline.ai cannot detect microscopic perifollicular inflammation. However, the inflammation that causes the peripilar sign eventually leads to follicle miniaturization, which reduces measurable density. When peripilar signs appear on trichoscopy, your AI home readings may still look stable because the process has not yet produced visible density loss.
This is exactly why the combined approach works. Trichoscopy catches the process before density drops. AI tracking catches when the density actually starts declining. Together, they provide both early warning and ongoing measurement.
If your dermatologist notes peripilar sign on trichoscopy, increase your myhairline.ai reading frequency to biweekly. Watch for the first density dips in the affected zones. When they appear, you have documented evidence of when the trichoscopy finding translated into actual density loss.
Yellow Dots and Empty Follicle Counts
Yellow dots are one of the most specific trichoscopy markers for AGA. They appear as amber or yellow spots at follicular openings and represent follicles that have either miniaturized completely or ceased producing visible hair. The follicular opening remains, filled with sebum and keratinous material.
The density of yellow dots correlates with disease severity:
| AGA Stage | Yellow Dot Density | Implications |
|---|---|---|
| Early (Norwood 2-3) | Scattered, few per field | Follicles beginning to miniaturize |
| Moderate (Norwood 3V-4) | Moderate density | Significant miniaturization in progress |
| Advanced (Norwood 5-6) | High density | Many follicles non-productive |
| Severe (Norwood 7) | Very high density | Extensive follicular loss |
What AI Tracking Sees Instead
Where trichoscopy counts individual yellow dots, AI tracking measures the result: fewer hairs per zone. A scalp area with many yellow dots will register as lower density on myhairline.ai because those follicles are no longer producing countable hairs.
The correlation is direct. More yellow dots on trichoscopy means lower density scores on AI tracking for the same zone. If your dermatologist reports increasing yellow dots at your 6-month visit, your myhairline.ai trend should show a corresponding density decline in that zone over the same period.
Vellus Hair Predominance and Miniaturization Tracking
In healthy scalps, the ratio of terminal hairs (thick, pigmented, long) to vellus hairs (thin, light, short) is approximately 7:1. In AGA, this ratio shifts as terminal follicles progressively miniaturize into vellus follicles. A ratio below 4:1 is considered diagnostic for active AGA.
Trichoscopy quantifies this ratio by examining individual hairs under magnification. Dermoscopic images clearly show the diameter difference between terminal and vellus hairs, and software can count each type.
What AI Tracking Sees Instead
myhairline.ai detects miniaturization through its density and coverage algorithms. As terminal hairs convert to vellus hairs, two things happen that AI can measure:
- Density scores decline because vellus hairs contribute less to coverage than terminal hairs
- Scalp visibility increases as thin vellus hairs fail to conceal the scalp surface
The AI does not count individual vellus hairs, but the trend in density scores reflects the same process that trichoscopy measures at the follicular level. A gradual, steady decline in density scores without major shedding events strongly suggests ongoing miniaturization.
Hair Diameter Diversity as an Early Marker
Before vellus hairs outnumber terminal hairs, there is a transitional phase where a single scalp zone contains hairs of widely varying diameters. Trichoscopy calls this "hair diameter diversity" or "anisotrichosis." A zone with more than 20% variation in hair shaft diameter is considered positive for this finding.
This is one of the earliest detectable signs of AGA, often appearing before the patient notices any visual thinning. On trichoscopy, it looks like a mix of thick and thin hairs growing from adjacent follicles in the same region.
How This Appears in AI Tracking Data
In myhairline.ai, hair diameter diversity may initially produce inconsistent readings for the same zone. One session might read slightly higher because the camera caught a favorable angle on the thicker hairs, and the next session might read lower. If you see reading variability that was not present in your early baseline sessions, it may reflect increasing anisotrichosis.
This is another case where a trichoscopy visit provides the clinical confirmation for something your AI data hints at.
Building a Diagnostic Bridge Between Systems
The practical value of understanding these correlations is communication with your dermatologist. When you bring myhairline.ai data to a trichoscopy appointment, both of you can connect the microscopic findings to the macroscopic trends.
Here is how to organize your data for a clinical visit:
| What You Bring | What It Adds to Trichoscopy |
|---|---|
| 6-month density trend by zone | Shows rate of change between clinical visits |
| Zone-specific density scores | Identifies which areas are declining fastest |
| Treatment adherence log | Confirms whether medications were used consistently |
| Photo comparisons (same angle, same lighting) | Visual confirmation of density changes |
| Notes on shedding episodes | Helps distinguish telogen effluvium from AGA progression |
Your dermatologist performs trichoscopy and identifies the pathological findings. Your myhairline.ai data shows the timeline and rate of the resulting density changes. Together, the diagnosis is more complete and treatment decisions are better informed.
Condition-Specific Finding Maps
Different hair loss conditions produce different trichoscopy finding patterns. AI tracking cannot differentiate between conditions, but knowing what your dermatologist found helps you interpret your density data correctly.
| Condition | Key Trichoscopy Findings | AI Tracking Pattern |
|---|---|---|
| Androgenetic alopecia | Yellow dots, peripilar sign, vellus predominance | Gradual density decline, worst at crown/temples |
| Alopecia areata | Exclamation mark hairs, black dots, yellow dots | Sudden zone-specific density drop |
| Telogen effluvium | Reduced anagen ratio, increased single-hair units | Diffuse density decline across all zones |
| Scarring alopecia | White dots, absent follicular openings | Permanent density loss in patches |
| Traction alopecia | Broken hairs, follicular erythema at margins | Density loss at hairline edges |
If you are using finasteride (80-90% halt further loss, 65% experience regrowth) or Minoxidil (40-60% moderate regrowth), your trichoscopy findings should improve over time. Your AI density trend should reflect that improvement as well. Discrepancies between the two merit discussion with your provider.
Limitations to Acknowledge
AI home tracking and clinical trichoscopy operate at fundamentally different scales. Trichoscopy examines individual follicles at 10-70x magnification. myhairline.ai analyzes standard photographs at 1x magnification.
This means AI tracking will always lag behind trichoscopy in detecting early changes. Perifollicular inflammation, early miniaturization, and shifts in anagen/telogen ratios are invisible to home photography until they produce enough macroscopic density change to register in the AI analysis.
The value of AI tracking is not in matching trichoscopy's diagnostic sensitivity. It is in providing continuous, quantified trend data that gives clinical snapshots context. A single trichoscopy finding of "increased vellus ratio" means more when paired with a 6-month AI trend showing exactly when and how fast density declined.
For a detailed comparison of these two approaches, see our trichoscopy versus AI analysis comparison. To improve your home photo quality for better AI readings, review our clinical hair loss photography standards.
Start building your density trend data today at myhairline.ai/analyze and bring quantified evidence to your next dermatology appointment.
This content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment.