Autumn hair loss: what science says — and what's actually worth taking
It starts in the shower drain. Then it's the brush, the pillow, the mark on the shoulder of a dark sweater. Every year, around September, thousands of people in Portugal search for the same thing with the same question behind it: is this normal, or is something going on? In the vast majority of cases, it's normal — and it's temporary. This article explains why, how to distinguish seasonal hair loss from hair loss that requires clinical investigation, and what makes sense to do in the coming weeks.
50–100
hairs per day is the range considered normal in most clinical sources
~3 months
is the delay between hair entering a resting phase in summer and falling out in early autumn
Is autumn hair loss real?
It's not just an impression, nor is it late-summer folklore. It's a measurable pattern, documented for decades in dermatological studies using trichograms and phototrichograms.
A benchmark study followed 823 healthy women over six years and showed a clear annual periodicity in hair growth and loss: the proportion of hairs in the resting phase — called telogen — peaks in summer, with a second minor peak in spring, and a minimum at the end of winter.
Later work, using phototrichograms in long-term follow-ups, places the highest percentages of telogen in August, September, and October, with minimum values in December, January, and February. A study with almost 2,900 participants over two consecutive years found the same pattern: more shedding between July and October, less in January.
In other words: the peak of hairs that enter a resting phase is in summer. The peak of hairs that fall out is in late summer and early autumn. That's why September is the month when everyone notices.
A relevant detail from the data: this seasonal variation appears regardless of whether the person already has male or female pattern hair loss. It is a biological rhythm that overlays everything else happening on the scalp.
The four pillars
Why hair falls out three months after summer
Four mechanisms explain almost everything observed in September — and, above all, explain why the phenomenon tends to resolve itself.
01
The follicle cycle
Each follicle goes through three phases: anagen (active growth, between two and six years), catagen (transition, two to three weeks), and telogen (resting, a few months, at the end of which the hair detaches to make way for a new one). At any given time, a portion of the hair is at rest — that's how the system works.
02
The photoperiod
The most cited hypothesis for seasonality is the solar shield: the body maintains a higher proportion of hair during the peak of summer, a time of greater radiation on the scalp. It is the same mechanism linked to day length that regulates fur shedding in mammals — an evolutionary echo that continues to function despite central heating.
03
The three-month delay
Hairs that enter telogen in summer do not fall out immediately. They remain at rest and are only released about three months later, which places the shedding exactly at the transition to autumn. The cause is in summer; the effect appears in September.
04
The false alarm of wash day
A hair that detaches from the follicle doesn't fall out immediately — it gets caught in the rest of the hair. Those who wash their hair every two or three days release all these hairs at once in the shower. The clump seems dramatic, but it corresponds to two or three days of accumulated normal shedding.
50–100 hairs per day
This is the reference range — and seasonal shedding is an oscillation, not a new baseline
Some dermatologists work with a wider range, from 50 to 150. Seasonal shedding adds a temporary variation to this baseline for a few weeks. To assess the evolution with some objectivity, it's always advisable to compare equivalent washing days — never a wash day with a day when there was only brushing.
Practical examples
What to do in the next six weeks
None of these measures stop hair loss that is already in progress — because, as explained below, that is not biologically possible. What they do is reduce noise and prepare the next growth cycle.
Test
Ferritin
Reflects iron stores. It can be low without the blood count indicating anemia — and goes unnoticed.
Test
25(OH)D
September is the month when reserves are at their highest point of the year. If the value is already low now, it will be worse in winter.
Test
TSH
Thyroid function is a common and often unidentified cause of diffuse hair loss.
Test
Complete Blood Count (CBC)
Completes the basic screening and contextualizes the ferritin value. It costs little and changes the conversation.
Routine
Less mechanical tension
Less tight ponytails, less aggressive brushing of wet hair, less direct heat.
Routine
Sufficient protein
Hair is keratin. In phases of marked caloric restriction, it is the first thing to protect.
Routine
Clean scalp
A scalp without flaking or irritation is the ground where new hairs grow.
Routine
Photographic record
The same part, the same light, once a week. It's the most honest way to assess evolution — memory isn't reliable.
Seasonal or clinical? How to distinguish
Seasonal hair loss is a form of telogen effluvium — the clinical term for diffuse hair loss that occurs when an unusual number of follicles enter a resting phase at the same time. The difference between the seasonal version and the version that requires investigation lies in the pattern, duration, and density.
Seasonal Hair Loss Hair Loss that Deserves Evaluation Duration A few weeks; tends to stabilize from October Many consecutive months, or progressively worsens Pattern Diffuse — uniform throughout the scalp Localized — receding hairline, crown, or bald spots Density Returns to the same point year after year The part widens; the scalp becomes visible Repetition Has happened in previous Septembers First time, or progressively worsening
It is advisable to seek medical evaluation when hair loss is accompanied by persistent fatigue, weight changes, cold intolerance, brittle nails with ridges, very heavy menstrual cycles, or when it occurred within two to three months following surgery, infection, childbirth, a very restrictive diet, or a period of intense stress.
Smart supplementation
Why most hair supplements don't solve this
Here's the inconvenient part for supplement sellers. Hair that has already entered telogen is disconnected from the dermal papilla and blood supply. It is biologically pre-programmed to detach. No shampoo, serum, or capsule will reattach it to the follicle.
The practical consequence is this: if someone starts a hair supplement today and hair loss stops within six weeks, there's no way to know if it was the supplement or the calendar — because that's exactly when seasonal effluvium resolves on its own. That's why these products seem to work so well in October and November.
This doesn't mean there's nothing to do. It means that the useful intervention is not to stop the ongoing hair loss: it is to ensure that the next growth cycle has raw material. Supplements are exactly that — a complement to a varied diet, never a substitute for it or for clinical evaluation.
Three micronutrients have authorized health claims in the European Union specifically for the maintenance of normal hair: zinc, selenium, and biotin. This is an important difference compared to most hair marketing — it means that the relationship with hair has been evaluated and accepted, not just asserted.
Most recommended
Nutrined
Hairformula 120 Caps
Combines in a single daily dose the nutrients with authorized claims for hair — zinc and biotin, which contribute to the maintenance of normal hair — along with B-complex vitamins and cystine, an amino acid present in the keratin structure. For those who prefer a combined approach instead of managing three separate bottles, it is the simplest option to maintain throughout autumn and winter.
How to use The manufacturer's recommended daily dose, continuously and integrated into a varied and balanced diet. Important note: high doses of biotin can interfere with thyroid tests and cardiac markers — it is advisable to suspend a few days before testing and inform the laboratory.
Complementary
Now Foods
Zinc Glycinate 30 mg
Zinc in chelated bisglycinate form, chosen for its good digestive tolerance. Zinc contributes to the maintenance of normal hair, the normal functioning of the immune system, and the protection of cells from undesirable oxidation.
How to use One capsule per day, with a meal. Do not exceed the recommended daily dose.
Complementary
Now Foods
Selenium 100 mcg
Selenium in L-selenomethionine, in a discreet daily dose. Selenium contributes to the maintenance of normal hair and the normal functioning of the immune system. Soil in Portugal is relatively poor in this mineral, which makes dietary intake more variable than supposed.
How to use One tablet per day, with food. Selenium has a narrow safety range — do not combine multiple sources without professional guidance.
Only with tests
Now Foods
Iron Complex
Iron combined with vitamin C, folate, and vitamin B12. Iron contributes to the reduction of tiredness and fatigue and to the normal formation of red blood cells and hemoglobin; vitamin C increases iron absorption. It is only appropriate when there is a confirmed deficiency in tests.
How to use According to the dosage indicated on the label and always with the guidance of a healthcare professional. Excess iron accumulates in the body — it should not be taken without prior tests.
Frequently asked questions
The questions that always come up in September
How long does autumn hair loss last?
Typically a few weeks. Trichogram data show that telogen percentages begin to decrease from October and reach a minimum in winter. If it persists for more than three months, it is no longer reasonable to attribute it to the season.
Does seasonal hair loss lead to baldness?
Not with seasonal hair loss. Density returns to the same point year after year. When the part progressively widens year after year, it is another type of hair loss and deserves dermatological evaluation.
Does biotin solve hair loss?
Biotin contributes to the maintenance of normal hair, but a real biotin deficiency is rare in those who eat a varied diet. Without a deficiency, supplementing adds nothing — and high doses interfere with thyroid tests and cardiac markers.
Does it make sense to take collagen for hair?
Collagen has no authorized health claims in the European Union for hair. Hair is keratin, not collagen. Ensuring total protein intake throughout the day has a more solid basis.
The useful intervention is not to stop the hair loss that is already in progress. It is to ensure that the next cycle does not find an empty reservoir.
September is a month when many people buy in a panic — and October is the month when almost everyone thinks the purchase worked. The calendar is generous with hair products. It's more worthwhile to use this time of year to do what is rarely done: measure. Ferritin, 25(OH)D, TSH, and a complete blood count cost little, take a morning, and transform a diffuse concern into an informed decision. If there's nothing to correct, that's good news. If there is, it was found at the right time — before winter, and in time for the next growth cycle.
Hair care with discernment
- Nutrients with authorized health claims for the maintenance of normal hair: zinc, selenium, and biotin
- Selected brands, with chelated forms and transparent compositions
- Advice from those who know the catalog — and know when the answer is "get tested first"
This article is for informational and educational purposes only and does not replace the evaluation of a doctor or other qualified healthcare professional. It is advisable to schedule a consultation if hair loss lasts more than three months, if it is localized instead of diffuse, if there are bald spots, redness, flaking, or pain on the scalp, or if associated general symptoms appear.
Food supplements should not be used as a substitute for a varied and balanced diet or a healthy lifestyle. Do not exceed the recommended daily dose. Keep out of reach and sight of children. In case of pregnancy, breastfeeding, diagnosed illness, or medication, consult a healthcare professional beforehand.
You receive this email because you subscribed to the Viva Saudável newsletter.
Viva Saudável · Maia, Portugal · vivasaudavel.pt
Comments (0)
There are no comments for this article. Be the first one to leave a message!