Can Damaged Hair Be Repaired?
What damages hair, and what actually keeps it healthy.
Updated 22 October 2026.
The short answer: no. The hair you can see is dead tissue, with no way to heal itself. Products can coat it, smooth it and protect it from further damage, but none of them turns damaged hair back into undamaged hair.
So healthy hair is not hair that has been repaired. It is hair that has been damaged less. Here is where that damage comes from.
- What damages hair
- Each one, explained
- Why it can’t heal
- Styling or damage?
- What treatments do
- The hair you haven’t grown yet
- Where Radico fits
What damages hair: a map
What a strand goes through adds up as damage per event × how often it happens × the years it stays on your head. Here is where everyday damage sits on those two scales, and the two places where what you use, not just how you use it, moves the dot.
Each one, explained
What it does to the strand, how often it tends to happen, and what lowers it.
Big, rare events
Chemical treatments that change the bonds holding hair together. Each one leaves a permanent mark on the strand.
Peroxide in an alkaline mix dissolves melanin, and with it oxidises disulfide bonds into cysteic acid, most heavily in the cuticle. The change does not reverse.
Lower it: space sessions out, and lighten only new growth rather than going over hair that is already lightened.
They break disulfide bonds on purpose so hair can be reshaped. Not all of them re-form, and relaxers are strongly alkaline.
Lower it: treat new growth only, and leave as long between treatments as you can.
An alkali swells the strand and lifts the cuticle so dye can get in, and peroxide develops the colour inside. It oxidises keratin along with the pigment. Because grey shows at the roots within weeks, this is the chemical event most people repeat most often.
Lower it: with a peroxide dye, colour the regrowth only. Or take colouring out of this group entirely: Radicoplant colour has no peroxide, ammonia or alkali. How it works ↓
Harsh and frequent
Heat, often daily. For people who style with heat every day, this is usually the largest share.
Direct contact at high temperature. Cuticle damage rises with temperature, and it is worst on hair that is still damp, where trapped water heats inside the strand.
Lower it: use the lowest setting that works, only on fully dry hair, and one pass rather than several.
In one study, surface damage rose as the dryer got hotter and closer. Held about 6 inches away and kept moving, it did less overall damage than leaving hair to dry on its own for hours.
Lower it: medium heat, keep it moving, keep it at a distance.
Small but constant, and the environment
Little each time, but it happens hundreds of times before your ends are cut.
Wet hair is swollen and stretches more easily, so friction chips the cuticle faster than when it is dry. Leaving hair wet for hours carries its own cost: in the same study, hair that took over two hours to dry showed damage inside the strand.
Lower it: blot or wrap instead of rubbing, detangle from the ends with a wide-tooth comb, and don’t leave it soaking for hours.
Water swells the strand, and handling during the wash wears the cuticle. An alkaline wash, such as a true soap, also leaves the cuticle slightly raised, so the hair is rougher until the pH comes back down.
Lower it: wash only as often as your scalp needs, and work shampoo into the scalp rather than scrubbing the lengths. After an alkaline wash, finish with an acidic rinse: RadicoHair Treatment Powder reads pH 3.2–3.5. More ↓
Ultraviolet light breaks down hair protein and pigment gradually over a season, which is why ends often feel drier and look lighter by autumn.
Lower it: a hat or scarf in strong sun.
Pool water is treated with chlorine, an oxidiser. Regular swimmers often notice rougher, drier ends.
Lower it: wet hair with tap water before swimming so it absorbs less pool water, wear a cap, and rinse straight after.
One exception to the drying advice: in the 24 hours after a plant colour that contains indigo, let hair dry slowly rather than with a dryer. The colour is still forming, and drying it fast changes the result. Our drying test →
Only one part of a hair is alive
Every item on that list stays on the strand, because the strand cannot heal. A hair has two parts: the follicle under the skin is living tissue, and the strand above it is not.
Has a blood supply and dividing cells, and builds new hair every day.
Packed keratin protein. No blood supply, no nerves, no cells that can divide or rebuild.
Skin heals because living cells replace damaged ones. A strand has none, so what happens to it stays. Damage leaves only one way: as the hair grows out and is cut off.
And your ends are older than you think
Hair grows about half an inch a month, and a single hair can keep growing for several years before it is shed.
Styling or damage? It depends which bond breaks
Not everything on the list is the same kind of change. Keratin is held in shape by several kinds of chemical bond. Some break and re-form every day without harm. One kind, once changed, never comes back.
Water: bonds break, then re-form
- DryHydrogen bonds hold the chains in place.
- WetWater slips between the chains. The bonds let go.
- Dry againThey re-form, in whatever shape hair is in.
This is why bed head is not damage. Sleep on damp hair and it dries pressed against the pillow; the hydrogen bonds re-form in that shape. Wet it again and it is gone. Blow-dry styling, rollers and humidity frizz all work the same way.
Bleach: bonds change for good
- HealthyDisulfide bonds give hair its strength.
- WetWater does not touch them.
- BleachedOxidised into cysteic acid. They do not re-form.
Bleach and peroxide dyes oxidise disulfide bonds into cysteic acid, a different molecule that does not turn back. That change stays in the strand until it is cut off. What peroxide does to the protein →
| Bond | What breaks it | Does it come back? |
|---|---|---|
| Hydrogen bonds weak, very many | Water, heat | Yes, as hair dries |
| Salt bonds moderate | Strong acids or alkalis | Largely, as pH returns to normal |
| Disulfide bonds strong | Perm lotion, bleach, peroxide dye | No, once oxidised to cysteic acid |
The first is styling. The last is damage, and no product undoes it. That is why the chemical group sits at the top of the map.
But wet hair is more vulnerable
Water does not damage hair by itself, but it changes how hair behaves. A wet strand swells, becoming noticeably wider while barely changing in length, and it stretches more easily. That is why rubbing wet hair with a towel or pulling a brush through it does more harm than the same handling when dry, and why heat on hair that is still wet is especially hard on it.
What treatments really do
If hair cannot heal, what are conditioners, masks and oils for? Mostly, they change the surface: how it feels, how it reflects light, and how easily it is damaged next. That is not repair, but it is not nothing either.
They coat, and that changes how hair looks
Silicones and oils fill in a rough surface and give it a smooth skin. Worn hair under a good coating can look and feel close to healthy hair, until the coating washes off. Nothing underneath has changed. Why shine is not proof of health →
They reduce friction, and that prevents damage
Damaged hair carries a negative charge on its surface. Conditioning ingredients carry a positive one, so they cling to it. The result is less tangling and less force on the cuticle every time hair is handled. It does not undo past damage, but it lowers the next round of the “small but constant” group on the map.
A few get inside
Most oils sit on the surface. Coconut oil is an exception that has been studied: in one laboratory comparison, it penetrated the hair and reduced the protein lost during washing, while mineral oil and sunflower oil did not. That is protection from the inside, not rebuilding.
“Bond repair” is still being argued over
Some products say they reconnect broken bonds inside the hair. The evidence is mixed, much of it comes from the companies that make them, and none of it shows hair returned to its original state. We would treat these claims as unproven for now.
A treatment cannot repair hair. A good one can help protect it.
The hair you haven’t grown yet
Everything above is about the strand. The other half of hair health is the living follicle, and it depends on the rest of your body.
- Nutrition. Real deficiencies, of iron or protein for example, can affect hair. Supplements are a different matter: there is little evidence they help people who are not deficient.
- Illness and major stress. A high fever, surgery, childbirth or a severe shock can push many follicles into their resting phase at once, followed by heavier shedding a few months later.
- Hormones. Menopause and other hormonal changes affect hair thickness and density.
- Tension. Very tight styles pulled hard for long periods can damage the follicles themselves.
If you are losing more hair than usual, or it is thinning in patches, that is a question for a doctor or dermatologist, not for a hair product. No cosmetic, including ours, treats the follicle.
The two green arrows on the map
You cannot repair the hair you have. You can choose what the next few years of it go through. If you cover grey, colour is the chemical event you repeat most often, and washing is the one you repeat most of all. These are the two places our products are built to change.
Colour Me Organic
- Plants and water only. Certified organic herbs across 24 shades. No peroxide, no ammonia, no PPD.
- Colour without opening the hair. Henna’s pigment bonds to keratin and indigo settles at the surface. Nothing in the pouch is there to change disulfide bonds.
- Builds with each use. Grey blends more fully over repeat applications.
- Checkable. Certified COSMOS ORGANIC by ECOCERT since 2012; every shade is in the public directory.
Hair Treatment Powder
Amla, reetha and shikakai, reading pH 3.2–3.5 in water. Used as a rinse after an alkaline wash, such as our Shampoo Bar, it brings the pH back down so the cuticle lies flat again instead of staying raised.
The arrow on the map is small on purpose. It lowers one part of what washing does; it does not make washing harmless, and it repairs nothing.
About the rinse →What neither one is. Neither is a treatment, and neither repairs what is already in your ends. Plant colour cannot lighten, grey takes it a little lighter and warmer, and results on bleached or permed hair are harder to predict. The habits in the list above still apply. Patch test 48 hours before every new shade. First-time customer assurance →
The point of this page, in one line: healthy hair is not hair that has been repaired. It is hair that has been damaged less.
What we have not measured
The science on this page comes from published research on hair in general, listed below. None of it involves Radico. The map at the top is our own qualitative summary of that research, not a measurement, and its two green arrows are based on what is in each formula.
We have not measured damage to hair coloured with Radico compared with other colours, or tested our products for any of the effects above. When we say Radico colour does not change disulfide bonds, that is a statement about the formula, not a measurement on hair. If we run that test, the result goes on this page whichever way it falls.
References
Robbins CR. Chemical and Physical Behavior of Human Hair. 5th ed. Springer; 2012. Hair structure, the bonds in keratin, swelling in water, the effects of bleaching, heat and grooming, and how conditioners adsorb to hair.
Rele AS, Mohile RB. Effect of mineral oil, sunflower oil, and coconut oil on prevention of hair damage. J Cosmet Sci. 2003;54(2):175–192.
Lee Y, Kim YD, Hyun HJ, Pi LQ, Jin X, Lee WS. Hair shaft damage from heat and drying time of hair dryer. Ann Dermatol. 2011;23(4):455–462.
American Academy of Dermatology. Hair care and hair loss guidance for the public. aad.org.
Radico Colour Me Organic and Hair Treatment Powder are cosmetic products for external use on hair. Nothing on this page is medical advice.