How do I tell breakage from hair loss?

Look at the root end. A shed hair has a small white bulb and is full length. A broken hair has no bulb, is shorter than the rest of your hair, and is often blunt or split at the break.

Can hard water damage hair?

It is the damage nobody suspects. Mineral deposition changes how hair behaves and compounds mechanical wear over time.

What heat is actually too much?

There are real temperature thresholds rather than a vague warning, and the article names them — along with what chlorine and chemical processing add.

Breakage or Hair Loss? How to Tell the Difference — and What Hard Water and Heat Are Doing to Your Hair

17. August 2026

By Dr. Susan Lin, MD | MD HAIR | La Cañada Ventures, Inc. — Scalp Health Series

Your ponytail is thinner. Not dramatically — but you can feel it when you wrap the elastic, and you're going around one extra time now. There's a fine halo of short pieces standing up around your part that you've been calling "new growth" and hoping is exactly that. Hair on the bathroom counter, hair on your sweater, hair on the pillow.

And underneath all of it, one question you can't answer: is my hair falling out, or is it breaking?

Nearly everyone gets this wrong, and the cost of getting it wrong is high — because the two problems have almost nothing in common. One is a follicle problem, driven by hormones, inflammation, nutrition, or illness, and treated at the scalp. The other is a fiber problem, driven by water chemistry, heat, chemistry, and mechanical force, and treated on the strand. Spend a year applying scalp serums to a breakage problem and you'll get nowhere. Spend a year on bond-building masks while a follicular process quietly progresses, and you lose ground you can't easily recover.

I'm Dr. Susan F. Lin, M.D. There's a way to tell the difference that takes about ninety seconds and costs nothing. Let me show you, and then walk through what's actually damaging your hair.

The Single Most Useful Test: Look at the Root End

Pick up one of the hairs and look at the end that came from your head. Hold it against a contrasting background — a white sheet of paper for dark hair, a dark countertop for light hair — in good light. Reading glasses or a phone camera on macro will help enormously.

A shed hair has a bulb. A broken hair does not.

What a shed hair looks like

A hair that was released by the follicle at the end of its cycle terminates in a small, pale, rounded swelling — the club hair bulb. It's typically white or translucent, slightly wider than the shaft, and smooth. That bulb is keratinized tissue from the base of the follicle, formed as the hair detached from its blood supply at the end of anagen.

If you're seeing bulbs, the hair completed its cycle and departed normally. This is shedding. Some quantity of it is entirely normal — 50 to 100 hairs a day is the conventional range — and the question becomes whether the volume is elevated and why.

One nuance: the bulb is not "the root," and seeing it does not mean the follicle came out. The follicle remains in your scalp. It is already building the next hair.

What a broken hair looks like

A broken hair ends in a blunt, jagged, or frayed tip with no swelling — it's the same width as the rest of the shaft, or splayed into split fibers. It simply stops.

Broken hairs also tend to be short, because they fractured mid-length. That halo of one-to-four-inch pieces around your part and hairline that you've been calling new growth? Look at the ends. New growth tapers to a fine point. Breakage ends bluntly.

Under magnification, damaged shafts sometimes show classic patterns: trichorrhexis nodosa, where the cortex frays outward at a weak point like the bristles of two brooms pushed together, and trichoptilosis, ordinary split ends (Whiting, 1987).

How to actually run the test

Collect hairs over one full day from your brush, drain, and pillow. Don't cherry-pick. Then sort them into two piles — bulbs and no-bulbs — and note lengths.

Mostly bulbs, mostly full length → shedding. A follicular process. Look at hormones, thyroid, ferritin, recent illness or stress, and pattern loss.
Mostly blunt ends, mostly short → breakage. A fiber problem. Look at water, heat, chemistry, and how you handle wet hair.
A meaningful mix → both, which is extremely common and worth saying plainly: the person who is anxious about shedding often starts styling more aggressively to disguise it, and adds a breakage problem on top of a shedding one.

There's a related distinction worth knowing: shedding is a quantity change, while pattern hair loss is a caliber change — hairs coming in progressively finer and shorter. Miniaturization doesn't show up in a drain count at all. It shows up as a widening part.

What Breakage Actually Is

A hair shaft is a composite structure: an outer cuticle of overlapping keratinized scales, an inner cortex of keratin bundles that provides essentially all of the tensile strength, and — in coarser hairs — a central medulla.

The cuticle is the armor. It is also finite and non-renewable. Hair is not living tissue; there is no repair mechanism, no cell turnover, no healing. Every scale lifted, chipped, or stripped is gone permanently, and the damage is strictly cumulative from the moment that segment of hair emerged from your scalp (Robbins, 2012).

Which is why breakage concentrates in the mid-lengths and ends: for shoulder-length hair, the ends are roughly two years old and have accumulated two years of washing, brushing, heat, sun, friction, and chemistry. The cuticle there is thin or locally absent, exposing the cortex, and once cortical fibers are exposed the shaft loses tensile strength and fractures under loads it would once have shrugged off.

Hard Water: The Damage Nobody Suspects

If you have hard water, you are running a low-grade chemical treatment on your hair every single day, and you almost certainly don't know it.

Hard water carries dissolved calcium and magnesium ions, and often iron and copper from plumbing. These interact with hair in two ways.

Mineral deposition. Metal ions bind to the negatively charged sites on the hair's surface — sites that increase in number as the cuticle weathers, meaning damaged hair attracts more mineral, which causes more damage. Deposits accumulate as a rough film that raises surface friction, dulls light reflection, makes hair feel coarse and "coated," and resists conditioning. A controlled study in the International Journal of Trichology found significantly reduced hair tensile strength after hard-water treatment compared with deionized water, framing hard water as a contributor to breakage (Luqman et al., 2018).

Surfactant interference. Calcium and magnesium react with anionic surfactants to form insoluble salts — classic soap scum — which lather poorly, deposit onto the shaft, and leave residue that requires more product and more manipulation to overcome.

Metal ions also catalyze oxidative reactions — one reason hard water accelerates color fading, and why copper in particular is the usual culprit behind the greenish cast some blondes develop with pool exposure.

What actually helps: a chelating or clarifying shampoo containing agents such as EDTA or phytic acid, used every one to three weeks — chelators bind metal ions and carry them off, which ordinary shampoo does not. A shower filter reduces some mineral load and is worth trying, though it won't fully soften water. A final rinse with cool filtered water, and a slightly acidic rinse or acidic conditioner to help re-flatten the cuticle after mineral exposure.

Do not clarify daily. Chelating shampoos are legitimately stripping, and using one every day trades a mineral problem for a lipid-depletion problem.

Chlorine and Swimming

Chlorine is an oxidizer. It degrades the shaft's lipid layer — particularly 18-MEA, the fatty acid that gives the cuticle surface its natural water-repellency and slip — leaving hair rough, porous, and dramatically more prone to tangling and breakage. It also oxidizes melanin, which is why swimmers' hair lightens and shifts brassy.

The green tint is not from chlorine itself but from copper, present in pool water from algaecides and plumbing, which deposits into porous hair and oxidizes.

The routine that works: wet your hair thoroughly with clean water before entering the pool — saturated hair absorbs far less pool water. Apply a leave-in conditioner or light oil as a barrier. Wear a cap. Rinse immediately after swimming, and use a chelating shampoo periodically through swim season.

Heat: The Temperature Thresholds That Actually Matter

Heat styling damage is not a matter of degree — it crosses genuine physical thresholds.

Around 150°C (about 300°F), the alpha-keratin helices in the cortex begin to denature. This is a structural change to the protein that gives hair its strength, and it is not reversible (Robbins, 2012).

Above roughly 200–215°C (390–420°F), keratin degrades outright, and lipid and melanin damage accelerate sharply.

Most consumer flat irons reach 230°C (450°F). That number was chosen for speed on the most resistant hair types, not for safety on yours. Fine, color-treated, or already-damaged hair has no business anywhere near it.

Two mechanisms make this worse than the temperatures alone suggest:

Bubble hair. If you apply high heat to hair that still holds significant water — a flat iron on damp hair, or a very hot dryer held close — the water inside the shaft can vaporize and expand, forming gas-filled cavities that blow the cortex apart from within. The affected segments are visibly beaded under magnification and are structurally ruined. Detwiler and colleagues documented this and reproduced it experimentally with an overheating dryer (Detwiler et al., 1994). This is the single most preventable form of heat damage, and the rule is simple: never put an iron on wet or damp hair.

Thermal cycling. Gamez-Garcia showed that repeated cycles of wetting and blow-drying crack cuticle scales through cyclical thermal and hydration stress — meaning frequency of styling matters independently of peak temperature (Gamez-Garcia, 1998). Ten passes at a moderate setting can do more harm than one pass at a higher one.

Lee and colleagues studied hair dryers directly and found damage increasing with both higher temperature and closer proximity, while noting that natural drying is not automatically gentler — prolonged wetness has its own cost, since the cell membrane complex swells and weakens with extended water exposure (Lee et al., 2011).

The practical protocol: towel-blot and air-dry to roughly 70% before any heat. Use a heat protectant every time. Keep a dryer on medium at 6 inches or more, moving constantly. Cap irons at 150–180°C (300–350°F) for most hair, lower for fine or color-treated. One pass per section. And build in genuinely heat-free days.

Chemical Processing

Bleach, permanent color, relaxers, and perms all work by deliberately breaking hair's internal bonds — that is the mechanism, not a side effect.

Bleach swells the shaft, lifts the cuticle to admit peroxide, oxidizes melanin, and in the process oxidizes keratin and strips lipids. It is the most damaging common service, and damage compounds with each round.

Permanent color requires alkaline swelling and peroxide, so even without lift it is not a neutral process.

Relaxers and perms cleave and re-form disulfide bonds — the strongest bonds in the fiber. Relaxers in particular carry a meaningful breakage risk when overlapped onto previously processed hair or left on too long.

The compounding effect is what causes disasters: bleached hair that is then flat-ironed daily in hard water is being attacked chemically, thermally, and mechanically at once, on a cuticle with no armor left. If you process chemically, something else has to give — usually the heat.

Traction Alopecia: Where Styling Stops Being Breakage and Becomes Permanent Loss

This section carries a genuine warning, and I want it read carefully.

Traction alopecia is hair loss caused by sustained mechanical tension on the follicle — tight ponytails and buns, braids, cornrows, weaves, extensions, locs, tight wigs, and repeated tension on the same zone over years. It typically appears at the frontal and temporal hairlines, sometimes with a preserved fringe of fine hairs at the very margin.

In its early stage, traction alopecia is reversible. The follicle is being stressed but is intact, and relieving tension allows recovery. Early signs include perifollicular redness, small bumps around follicles, scalp tenderness after styling, headaches from tight styles, and short broken hairs along the hairline.

But prolonged traction can become permanent. Sustained tension eventually produces follicular damage and fibrosis, and once the follicle is replaced by fibrous tissue it does not regenerate. Khumalo and colleagues, studying determinants of marginal traction alopecia, found significant associations with tension-generating styling practices — particularly styles applied to chemically relaxed hair, which combines mechanical and chemical insult (Khumalo et al., 2008). Billero and Miteva, reviewing the condition, emphasize the same clinical point: early intervention preserves follicles, and late-stage traction alopecia is a scarring end-state (Billero & Miteva, 2018).

If your hairline is receding and you wear tight styles, see a dermatologist now, not eventually. This is the one item in this article where waiting has a permanent cost. A dermatologist can assess whether follicular openings are still present and, if needed, biopsy to determine whether scarring has begun. Traction alopecia — like seborrheic dermatitis, psoriasis, and the primary scarring alopecias — is a medical condition requiring dermatologic care. No cosmetic product, mine included, reverses a scarred follicle.

Practically: rotate styles and tension zones, keep protective styles for no more than six to eight weeks, avoid tension on chemically processed hair, never accept pain or bumps as normal, use fabric-covered or coil elastics rather than tight bands, and sleep with hair loose or very loosely secured.

Protein and Moisture Balance: What It Means, and What It Doesn't

Hair needs both structural reinforcement (protein-derived ingredients — hydrolyzed keratin, wheat or silk proteins, amino acids) and plasticizing hydration (humectants and emollients — glycerin, panthenol, fatty alcohols, oils, cationic conditioning agents).

Small hydrolyzed proteins can adsorb to the shaft surface and penetrate damaged regions, temporarily filling cuticle gaps and measurably improving tensile properties (Gavazzoni Dias, 2015). This is genuinely useful for damaged hair — but the effect is cosmetic and temporary. It washes out. It does not repair anything permanently, because hair cannot be repaired.

The imbalance states are real and recognizable:

Protein-heavy: stiff, straw-like, brittle, snaps rather than stretches, feels rough when wet. Too much protein without sufficient plasticizer makes a rigid, fracture-prone fiber. Back off protein treatments, increase moisture.
Moisture-heavy: limp, mushy, over-elastic — stretches like gum when wet and doesn't spring back, no definition. Increase protein, reduce heavy emollients.

Healthy, minimally processed hair often needs very little protein. Heavily bleached or relaxed hair may need it weekly. Test by feel rather than by rule.

Where this connects to everything above: a well-formulated conditioner is not a luxury step on damaged hair. Its most important function is reducing friction so the shaft survives detangling — and wet hair is where most breakage is actually generated, which is the subject of the mechanism spotlight below.

The Bottom Line

Look at the root end. A shed hair has a small pale bulb; a broken hair has a blunt or frayed end and is usually short. That ninety-second observation tells you which of two unrelated problems you have.

If it's shedding, the answer is at the follicle: hormones, thyroid, ferritin, recent illness, stress, or pattern loss — and a physician, labs, and a scalp-directed strategy.

If it's breakage, the answer is on the fiber, and the culprits are identifiable. Hard water depositing minerals that roughen the surface and weaken the shaft. Chlorine stripping the lipid layer. Heat past 150°C denaturing keratin, with bubble hair when tools meet damp hair and cumulative cracking from repeated cycles. Chemical processing that breaks bonds by design. And mechanical force — most of it applied to swollen, softened, wet hair with a comb and a towel.

Hair cannot heal. Every improvement in a breakage problem comes from preventing the next insult and cosmetically supporting what's already grown. That's not a limitation to be discouraged by; it's a clear instruction. Lower the temperature, chelate the minerals, cut the friction, and let new growth come in undamaged.

And if your hairline is receding under tight styles, please treat that as the medical matter it is, today. Traction is the one item here that runs out of reversibility.

Dr. Susan Lin's Clinical Perspective

"I ask patients to bring me the hairs. Not a description — the actual hairs, on a piece of paper. In a remarkable number of cases the answer is visible in seconds: a pile of short, blunt-ended fragments from someone who has been buying scalp serums for a year, or full-length bulbed hairs from someone who has been buying bond builders. Those are opposite problems with opposite solutions, and the anxiety that drives people to style harder to hide thinning is exactly what turns one into both. My rule is to identify the fracture point before spending another dollar. If it's the fiber, the wins are unglamorous and reliable — chelate the hard water, drop the iron below 180°C, never touch damp hair with heat, and treat wet hair as the fragile material it actually is. And if the hairline is receding under tension, that is a dermatologist's appointment this week, because traction alopecia does not stay reversible forever."

— Dr. Susan F. Lin, M.D., Physician Formulator, MD HAIR

Mechanism Spotlight: Why Wet Hair Breaks

The most consequential fact in fiber care is that hair changes its mechanical properties when wet. Dry hair's stiffness comes substantially from hydrogen bonds between keratin chains in the cortex — weak individually, enormously numerous collectively. Water molecules penetrate the fiber and disrupt those bonds, and the shaft swells radially, softens, and becomes markedly more extensible: it stretches further under a given load and enters plastic, non-recoverable deformation sooner (Robbins, 2012). Simultaneously, the swollen cuticle scales lift slightly at their free edges, raising surface friction so strands snag on each other rather than sliding apart. The combination is unforgiving. A comb dragged through wet, tangled hair meets high friction and a softened cortex at exactly the same moment — which is why so much breakage is generated in the few minutes after a shower rather than during the wash itself. This is also the mechanistic case for conditioner: cationic conditioning agents deposit on the negatively charged, weathered surface and reduce combing friction substantially, so the force required to detangle drops below the fracture threshold of a compromised shaft (Gavazzoni Dias, 2015). And it explains why heat on damp hair is uniquely destructive — a softened, water-laden fiber flash-heated past the boiling point of its internal water produces the cavitation of bubble hair (Detwiler et al., 1994).

MD HAIR Product Recommendation

MD® Revitalizing Treatment Conditioner

If your ninety-second test came back as breakage, the conditioner is not the optional step — it is the intervention. Most breakage is generated in the minutes after the shower, when a swollen, softened shaft meets high surface friction and a comb, and the single most effective thing you can do is lower that friction below the fracture threshold.

That is what MD® Revitalizing Treatment Conditioner was formulated to do. It is designed to deposit on weathered, mineral-roughened, negatively charged hair to restore slip, improve wet detangling, and support the look and feel of the shaft on hair that has been through hard water, heat, and processing. Apply it to mid-lengths and ends — never the scalp, where heavy conditioning agents add to follicular congestion — and detangle with it still in, with a wide-tooth comb, working from the ends up. Pair it with the MD® Nourishing Treatment Shampoo when you want the full system.

Formulated by Dr. Susan F. Lin, M.D. under the MD® mark (U.S. Reg. No. 4,471,494), physician-formulated since 2008, and manufactured in FDA-registered, GMP-compliant facilities in the USA.

Alongside it: MD Nutri Hair™

A conditioner protects the shaft you already have. It does nothing for the follicle building the next one, and where breakage is layered on top of genuine thinning, that second half matters. MD Nutri Hair™ carries standardized lilac verbascoside — the molecule that, in laboratory studies on human dermal papilla cells, reduced the release of pro-inflammatory signals including IL-1α, IL-6, IL-1β and TNF-α, and prevented testosterone-induced death of those cells (cell studies, not human trials; the authors say clinical study is still needed). One capsule daily, alongside the topical care that keeps the fiber intact. In a 30-day in-office consumer use study of MD Nutri Hair™ in 30 subjects, 95% saw improved hair appearance, 90% reported better manageability, and 75% reported increased fullness — self-reported, with no placebo control. Individual results vary — and those figures are the supplement's, not the conditioner's.

Genuine MD HAIR™ and MD Nutri Hair™ products are sold only through mdhair.com, md-factor.com, and the official La Cañada Ventures, Inc. stores on Amazon and Walmart. Purchases from other sellers cannot be authenticated.

Learn more about building a complete scalp and hair routine at mdhair.com/pages/scalp-health-guide

References (click to check)

Dr. Susan F. Lin, M.D. is the physician formulator behind MD HAIR, a line of drug-free hair and scalp products by La Cañada Ventures, Inc., physician-formulated since 2008. MD HAIR™ and MD Nutri Hair™ products are cosmetics and dietary supplements; they are not intended to diagnose, treat, cure, or prevent any disease. This article is for educational purposes and does not constitute medical advice. Traction alopecia, seborrheic dermatitis, psoriasis, and scarring alopecias are medical conditions requiring evaluation by a board-certified dermatologist — and in the case of traction and scarring alopecias, early evaluation is critical to preserving follicles.

Pregnancy and breastfeeding: because there are no clinical data in pregnant or breastfeeding women, we do not advocate using MD HAIR products during pregnancy or lactation.

MD Nutri Hair™ is a dietary supplement. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.