Damaged hair shows ten specific signs: split ends, breakage along the lengths, a rough feel, permanent tangles, excessive porosity, loss of elasticity, persistent frizz, dead shine, colour that bleeds out and styling that no longer holds. They all tell the same story: an open cuticle and a depleted keratin structure. Two simple tests, done at home in five minutes, will confirm the diagnosis.
The 10 signs of damaged hair
- Split ends. The fibre splits at its tip, for want of a cuticle.
- Breakage along the lengths. Short, uneven broken hairs, with no white bulb.
- Rough feel. Hair catches under your fingers instead of sliding.
- Permanent tangles. Lifted scales grip one another.
- Excessive porosity. The fibre drinks water instantly and dries abnormally fast.
- Lost elasticity. A wet hair pulled taut snaps or stays stretched out of shape.
- Persistent frizz. It shows up even in dry weather.
- Dead shine. Light scatters instead of reflecting.
- Colour that fades fast. The fibre no longer holds pigment.
- Styling with no hold. The blow-dry drops, the curls fall out.
Five signs or more ticked off: your hair is asking for a structured protein supply, not just a nourishing treatment.
Signs 1 to 4: what you can see and feel
These four signs are the easiest to spot, and the most often misread.
Split ends (trichoptilosis) appear when the cuticle is so eroded that the fibre splits in two. It is the one form of damage no product reverses: an uncut split travels up the hair. A micro-trim of one to two centimetres stops it going any further.
Breakage is identified by the short broken hairs sticking out along the lengths. One point of caution: a hair that falls out with its white bulb belongs to the natural cycle, not to breakage. If you are losing a lot of whole hairs, that is a different subject, covered in our article on seasonal hair shedding.
A rough feel and tangles go together. A cuticle with lifted scales looks like an open pine cone: it catches on neighbouring hairs, forms knots, and the vigorous brushing that follows causes even more breakage. Detangling therefore has to become a care step in its own right, with conditioner applied to the lengths and detangling that always starts at the ends.
Signs 5 and 6: the two tests to do at home
These two signs can be checked objectively in five minutes, with no equipment.
- Elasticity test. Gently stretch a wet hair between two fingers. Healthy hair lengthens then springs back. Damaged hair snaps or stays stretched out of shape, like a worn-out elastic band.
- Porosity test. Drop a clean, naturally shed hair onto the surface of a glass of water. If it sinks quickly, the cuticle is wide open. This test gives an indication, not a measurement: product residue or sebum will skew it. The full method and the three porosity profiles are set out in our article on porosity.
These two signs reflect a structure full of gaps. This is where a concentrated deep treatment such as the /REPAIR Intensive Repair Mask comes into its own: hydrolysed keratin fills the gaps, while shea butter and wheat proteins restore suppleness.
Signs 7 to 10: the knock-on consequences
The last four signs follow mechanically from the earlier ones.
- Frizz comes from an open cuticle that lets moisture in from the air: the hair swells unevenly and stands up. The full protocol is in our anti-frizz article.
- Loss of shine is not a missing ingredient but an optical phenomenon: a smooth cuticle reflects light, a lifted cuticle scatters it.
- Colour that bleeds out signals a porous fibre, unable to hold pigment just as it can no longer hold water.
- Styling that does not hold reflects a loss of shape memory: it is the internal keratin bonds that let hair keep the shape you give it.
Dry hair or damaged hair?
The distinction completely changes your care strategy.
| Dry hair | Damaged hair | |
|---|---|---|
| What is missing | Water and lipids | Protein within the structure |
| State of the structure | Intact | Damage to cuticle and cortex |
| What fixes it | Humectants and lipids | Protein, then moisture |
| Time to visible change | A few applications | Four to six weeks |
Damaged hair is almost always dry. The reverse is not true.
The repair protocol, in order
- Cut only what you must. One to two centimetres if splits have set in, no more.
- Pause the damage. No irons during the repair phase, hairdryer on moderate heat, loose hairstyles.
- Supply protein twice a week. A mask concentrated in hydrolysed keratin, 5 to 10 minutes on towel-dried hair. Useful processing time is explained in our article on how long to leave a mask on.
- Seal it in daily. A leave-in such as the /REVEAL Mist protects the fibre between washes.
- Switch to maintenance after four to six weeks. One mask a week is enough from then on.
The two key steps of the intensive phase come together in the /REPAIR + /REVEAL Repair Duo. To settle into the full routine afterwards, our four-step guide covers what comes next.
Damaged hair: the essentials
- The ten signs point to a single problem: open cuticle, depleted keratin.
- Split ends are the only irreversible damage. Everything else can be corrected.
- Damaged hair needs protein, dry hair needs water and lipids.
- Softness returns within a few applications, strength within four to six weeks.
- A porous fibre holds pigment poorly: strengthen before you colour.
Frequently asked questions about damaged hair
Can damaged hair really be repaired?
Hair is non-living matter: it does not heal. Hydrolysed keratin treatments fill the gaps, close the scales back down and restore strength, suppleness and shine very noticeably, but the effect has to be maintained. Only established split ends have to be cut.
Should you cut before starting a repair protocol?
A micro-trim of split ends is recommended, because an uncut split keeps travelling upwards. There is no need, however, to sacrifice whole lengths: the rest of the hair strengthens very well with care.
How often should you use a repair mask?
Once or twice a week, five to ten minutes on towel-dried lengths. Beyond that, effectiveness does not increase: the fibre absorbs a limited quantity of actives per application. Regularity beats quantity.
Can damaged hair still be coloured?
Better to strengthen the fibre for three to four weeks before colouring. A porous fibre absorbs pigment unevenly and the result will be neither true to tone nor long-lasting. Tell your hairdresser about the condition of your lengths.
How long does it take to get healthy hair back?
Softness returns from the first few uses, breakage drops noticeably within four to six weeks, and the fibre finds a lasting balance within two to three months, the time it takes for the most fragile lengths to be strengthened or replaced.
Is the glass of water test reliable?
It gives a useful indication, not a validated measurement. The result depends heavily on how clean the hair is and on the surface tension of the water. Always cross-check it against the elasticity test and what you observe when drying.
Sources
- Robbins C. R., Chemical and Physical Behavior of Human Hair, 5th edition, Springer, 2012.
- Gavazzoni Dias M. F. R., "Hair Cosmetics: An Overview", International Journal of Trichology, 2015.
- Lee Y. et al., "Hair Shaft Damage from Heat and Drying Time of Hair Dryer", Annals of Dermatology, 2011.
Article written by the KERA NEXT editorial team from the cosmetology literature cited. It is not a substitute for medical advice. Individual results: the outcome may vary depending on the nature and condition of your hair.