Telogen effluvium peaks in October and November in the northern hemisphere, making autumn and early winter the most common time for people to panic about hair loss. The density dip is real, but misinterpreting a seasonal shed as treatment failure leads to unnecessary protocol changes that can actually set back your progress.
Why Autumn and Winter Trigger More Shedding
Summer UV exposure pushes a larger percentage of hair follicles into the telogen (resting) phase. Because the telogen phase lasts approximately 3 months, those follicles begin shedding in October and November. This is a well-documented biological pattern, not a disease process.
| Season | Telogen Percentage | Shedding Level | Notes |
|---|---|---|---|
| Spring (Mar-May) | 10-12% | Baseline | Normal shedding levels |
| Summer (Jun-Aug) | 10-12% | Baseline | UV triggers future shed |
| Autumn (Sep-Nov) | 15-20% | Peak shedding | 3-month lag from summer UV |
| Winter (Dec-Feb) | 12-15% | Elevated | Gradual return to baseline |
Studies show that up to 10% more follicles enter telogen during this period compared to spring baseline. For someone with 100,000 follicles, that translates to an extra 5,000-10,000 hairs shed over 6-8 weeks.
Seasonal Dip vs. Treatment Failure: The Tracking Difference
The only reliable way to separate seasonal variation from genuine loss is year-over-year comparison. A single month-to-month density reading during autumn will almost always look worse, even on effective treatment.
Signs of a seasonal dip:
- Density drops 5-10% between September and November
- The pattern matches the same period from the previous year
- Recovery begins by January or February
- Hair pull test normalizes within 8 weeks
Signs of actual treatment failure:
- Density declines steadily across 3 or more months without recovery
- Year-over-year comparison shows lower density than the same month last year
- Miniaturization increases in tracked zones
- No recovery pattern by March
How to Build a Seasonal Baseline
Effective seasonal tracking requires at least 12 months of consistent data. The process is straightforward but depends on timing consistency.
Step 1: Take density readings at the same scalp zones every 2-4 weeks using consistent lighting and angles.
Step 2: After 12 months, overlay monthly readings to identify your personal seasonal pattern. Most people see their lowest density in October or November.
Step 3: In year two and beyond, compare each monthly reading against the same month in year one. This year-over-year comparison eliminates seasonal noise.
| Tracking Metric | Month-to-Month | Year-over-Year |
|---|---|---|
| Reliability for seasonal adjustment | Low | High |
| False alarm rate | High (autumn) | Low |
| Minimum data needed | 1 month | 12 months |
| Best use case | Acute events | Treatment efficacy |
When Seasonal Data Should Change Your Protocol
Tracking data across multiple autumn cycles can reveal whether your seasonal shed is within normal range or unusually severe. Some dermatologists use this data to recommend preventive measures.
Options some patients discuss with their doctors before autumn:
- Adding PRP sessions ($500-$2,000 per session) in September to boost density ahead of the shed
- Ensuring minoxidil compliance is at 100% during the September to December window
- Starting or adjusting finasteride dosage (which halts further loss in 80-90% of users)
The key principle is that protocol changes should be based on multi-year data patterns, not a single bad month. One autumn dip is expected. Two consecutive years of worsening autumn dips compared to baseline suggest a real problem.
Track Your Seasonal Pattern with AI
Stop guessing whether your autumn shed is normal. Upload a photo at myhairline.ai/analyze to get a date-stamped density baseline you can compare against next season.
This article is for informational purposes only and does not constitute medical advice. Consult a board-certified dermatologist for diagnosis and treatment of hair loss conditions.