Guides
Hair care, made simple
The short answer first. Then what to do, the numbers behind it, and the myths to ignore.
- DETANGLING How to brush and detangle your hair Most breakage comes from knots, not the comb. Add conditioner, start at the ends, and use a wide-tooth comb. Read the guide →
- CONDITIONER How to use conditioner properly Conditioner makes hair slippery so it snags and breaks less. Use it on lengths and ends, not the scalp. Read the guide →
- CURLS Curly and wavy hair care, simply Wash the scalp, condition the lengths, handle curls wet, and let gel set. A short routine for waves, curls and coils. Read the guide →
- DAMAGE Hair damage and repair Damage cannot be healed, only reduced, smoothed or cut off. What bleach, heat, bond builders, oils and trims really do. Read the guide →
- SCALP Dandruff and itchy scalp, explained Dandruff is a reaction to a yeast, not dry skin or dirt. What works, how long to use it, and when to see a doctor. Read the guide →
- HAIR LOSS Hair loss: the basics Shedding versus balding, how pattern loss works, what has trial numbers behind it, and why acting early matters. Read the guide →
- HEAT STYLING Heat styling without frying your hair Heat damage rises with temperature, time and repeat passes. Dry hair first, go as low as you can, and pass as few times as possible. Read the guide →
- WASHING How often should you wash your hair? Wash when your scalp is oily, itchy or flaky. That is every 1 to 2 days for straight hair and about weekly for coily hair. Read the guide →
- DRYING How to dry your hair without damaging it Wet hair is about half as stiff as dry hair. Blot, never rub, and keep any heat low, far away and moving. Read the guide →
- SLEEP How to protect your hair while you sleep Wet hair is fragile and tight styles pull. Here is what actually helps at night, and what silk pillowcase claims leave out. Read the guide →
Deep dives
Everything, in depth
Longer pages for when you want the full science.
Topics Everyday hair care in depth · 75
- Acidic rinses and product pHMildly acidic hair products make sense on chemistry grounds, but no trial shows that vinegar rinses or a particular pH reduce breakage.
- Androgens, anabolic steroids and hairTestosterone and other androgens thicken beard and body hair but can start or speed up pattern hair loss in people who are genetically prone.
- Antiandrogen comparison for hair lossA side-by-side of the drugs, topicals and supplements that work on the androgen pathway, with who they were studied in and how strong the evidence is.
- Beards and eyebrowsBeard preferences depend on context and what is fashionable, even beards beat patchy ones, and cosmetic options such as minoxidil for beards and microblading for brows rest on small studies.
- Bleach and colour damageBleaching and permanent dyeing chemically damage the hair fibre in every hair type, and most of that damage cannot be undone.
- Bond builders (Olaplex, K18, maleic acid, "acidic bonding")Bond builder is a marketing label for four unrelated chemistries; all have lab results on cut hair and none has a trial on real heads.
- Brushing and detanglingMost combing damage comes from tangles, so conditioner and the right technique cut breakage more than the choice of brush.
- Caring for hair by porosityMatching products to low, normal or high porosity is common advice, but almost none of it has been tested in people.
- Cosmetic hair growth serumsOver-the-counter serums, shampoos and tonics for thinning hair can be low-risk add-ons, but none has evidence close to minoxidil or finasteride.
- Curl patternHow straight, wavy, curly or coily your hair is gets decided in the follicle, mostly by genes, and it shapes shine, tangling, breakage and how a routine should be built.
- DHT and pattern hair lossPattern hair loss happens when genetically sensitive scalp follicles respond to the hormone DHT by shrinking a little more with every hair cycle.
- Diet and hairCrash diets and rapid weight loss cause shedding, ordinary diets rarely do, and testing beats guessing before you buy supplements.
- Double shampooing and wash techniqueThere is almost no trial evidence on how to shampoo, so the sensible default is one gentle wash on the scalp, with a second only after heavy buildup.
- Drug-induced hair changesMedicines can thin hair, regrow it curly, darken or whiten it, or lengthen lashes; this table sorts the best-known links by how strong the evidence is.
- Dry shampooDry shampoo soaks up surface oil so roots look fresher, but it does not clean your scalp and there are almost no studies on regular use.
- Exercise and hairThere is no human evidence that exercise causes or prevents pattern hair loss; under-fuelling is the bigger risk.
- FrizzFrizz comes from a rough, damaged surface and moisture uptake; products manage it, while less damage prevents it.
- Gray hair and premature grayingGraying is mostly genetic, but single-hair mapping shows some gray hairs can regain colour, and the famous stress-causes-gray mechanism has only been proven in mice.
- Hair and attractivenessIn rating experiments, how much hair you show, how gray it is and how aligned and undamaged it looks change how old, healthy and attractive you appear, while color and beards matter less and depend on context.
- Hair by ancestry, what differs and what overlapsHair differs on average between populations in curl, width, density and surface lipids, but the overlap is large and the old three-box labels hide more than they show.
- Hair colour for looksGray hair lowered attractiveness ratings in image swaps and blonde versus brunette results conflict; dyeing damages hair, PPD allergy is the real dye risk, and personal dye use has not been shown to cause cancer.
- Hair damage: what it is and where it comes fromDamage is cumulative and cannot be biologically healed, and chemical treatments, heat, sun, water and grooming each add to it.
- Hair densityDensity is how many hairs grow per square centimetre of scalp; it varies with ancestry, scalp site and age, and on its own it says little about hair loss.
- Hair dryingAir drying is not clearly safer than moderate-heat blow-drying; high heat, close range and heat on wet hair are the real problems.
- Hair elasticity and the home stretch testHair stretch and strength fall with damage, but the popular home stretch test has never been validated.
- Hair growth pipeline (2026)What is in clinical trials for hair loss as of October 2026, how far along it is, and how much to trust the early numbers.
- Hair loss scales, hairlines and how to classify your own hair lossThe Norwood, Ludwig, Sinclair and BASP scales describe pattern hair loss in broad bands, and this page explains how reliable they are, how well people can stage themselves and how to tell a mature hairline from a receding one.
- Hair loss treatment ladderAn evidence-ranked ladder of options for pattern hair loss in men and in women, with doses as studied and links to the studies, plus where to go for other causes of hair loss.
- Hair myths, checkedTwenty-five popular hair beliefs checked against the evidence, from shaving to biotin to baldness genes.
- Hair porosityPorosity describes how easily water moves in and out of a hair fiber; in practice it is mostly a marker of damage, and the popular float test does not measure it.
- Hair structure, from follicle to fiberThe hair you see is dead, hardened keratin made of three layers, which is why care is about protecting it rather than repairing it.
- Hair typing systemsSystems like 3B, LOIS and FIA put a name on your hair, but almost none have been tested for reliability, so use them as a convenience rather than a diagnosis.
- Haircuts and face shapeHair changes how a face is read, but the advice to pick a cut by face shape or facial ratios is stylist tradition that nobody has tested.
- Hairstyle preferences (what people find attractive)Rating studies say healthy, dense, shiny hair beats any named style, while claims about which men's cut women prefer have almost no peer-reviewed support.
- Hard water and hairHard water leaves calcium on hair and can irritate skin, but there is no good human evidence that it causes hair loss, and chelating shampoos are untested in trials.
- Heat damage and heat protectantsHeat on wet hair is the clearest harm, and there is little independent evidence that retail heat-protectant sprays work.
- Heat styling toolsFlat irons, curling tools and hot combs damage hair more with higher temperature, repetition and wet hair; dermatologists advise using them about once a week or less.
- How conditioner worksRinse-off conditioner coats hair with a positively charged layer that cuts friction and tangling; it does not repair structural damage.
- How often to wash your hairYour scalp sets how often you need to wash and your hair lengths set how rarely you can, so the right number depends on your hair type and scalp.
- How shampoo worksShampoo is water plus a blend of cleansing molecules that lift oil off your scalp and hair, and the blend matters far more than any single label word.
- How to work out your hair type at homeA step-by-step guide to describing your own curl, thickness, density, damage and scalp, using questions that research suggests people can answer reliably.
- Humectants and humidityHair swells and softens with humidity, but the popular rules about glycerin and humidity have not been tested; panthenol is the humectant with the best fibre data.
- JAK inhibitors and hairJanus kinase (JAK) inhibitors are pills that regrow hair in severe alopecia areata, but they are not treatments for ordinary pattern thinning.
- Leave-ins, masks and layering methodsMasks and leave-ins use the same conditioning chemistry as rinse-off conditioner; layering methods like LOC rest on consumer satisfaction, not trials.
- Minoxidil forms comparedSolution, foam, oral tablets, sublingual and extended-release minoxidil deliver the same drug in different ways; this page compares them.
- Natural remedies for hair growthNo natural remedy has strong evidence for growing hair, and the real value of most oils and plant extracts is cosmetic.
- Oils and hairOils coat hair and some enter it, which can cut damage from washing, but they do not repair split ends or add moisture.
- Post-finasteride syndromeSome men report sexual, mental and physical symptoms that start on finasteride and last after stopping; whether it is a distinct drug-caused condition is still unresolved.
- Prostaglandins and hairProstaglandins are fat-derived signals that switch follicles on or off; eye drops that copy one of them grow eyelashes but have not worked on the scalp.
- Proteins and hairHydrolysed proteins can modestly strengthen damaged hair in the lab, but the popular protein-moisture balance rule has never been tested.
- Relaxers, perms and smoothing treatmentsChemical straighteners and perms all damage hair, and some carry scalp, respiratory, kidney or cancer-association concerns worth knowing before you book.
- Scalp health and oxidized sebumSebum, scalp microbes and inflammation clearly drive dandruff, but there is no human evidence that scalp buildup or oxidized sebum causes hair loss.
- Scalp massageFree and harmless, but the only human evidence is a nine-man study without a control group.
- Sebum and scalp typesHow oily your scalp is depends mainly on androgens, age and sex rather than how often you wash, and a dry, flaky or itchy scalp is usually a barrier or yeast problem, not an oil shortage.
- Shampoo pHHair and scalp prefer mildly acidic conditions, but most shampoos are less acidic than that and the case for lower pH rests on lab mechanism rather than wear trials.
- Shampoo types and how to chooseShampoo types are marketing labels built from the same few parts, so choose by your scalp problem first and your hair type second.
- Silicones in hair careSilicones coat hair to cut friction and add shine without repairing it; buildup is real but manageable, and the scare claims are unsupported.
- Sleep surfaces and hairSilk and satin pillowcases are a plausible way to cut friction and tangles, but no human trial shows they prevent breakage or hair loss.
- Smoking, alcohol and hairSmoking goes with early graying and probably earlier pattern loss, but the evidence is observational and mixed.
- Split ends and trimmingSplit ends cannot be repaired, only smoothed over or cut off, and trimming preserves length by stopping splits travelling up the strand.
- Strand thicknessThickness is the width of a single hair strand, separate from how many strands you have, and it changes how hair feels, styles, breaks and ages.
- Stress, sleep and hairMajor stress can trigger temporary shedding, while everyday stress and poor sleep are weaker, mostly associational links.
- Styling products explainedStyling products come down to how much hold and how much shine you want; there are almost no head-to-head trials, so this page combines formulation knowledge with the few things that have been measured.
- Styling techniques for curly and wavy hairGentle, moisture-focused handling of curly hair is well supported, but specific techniques and the Curly Girl Method as a package have never been tested.
- Styling techniques for menNo trial tests how to style men's hair, so these blow-dry, product and clipper techniques are professional practice, labelled as such, with damage advice from dermatology.
- Styling techniques for womenNo trial tests how to style women's hair, so these blow-dry, heatless and low-tension techniques are professional practice; the perception studies say healthy-looking hair beats any specific style.
- Swimming, chlorine and green hairHeavy swimming can strip and discolour hair, and green tints usually come from copper rather than chlorine itself.
- Taking a good hair photoA well-taken photo shows curl family, length, hairline shape and overall hair loss pattern, but it cannot show strand thickness, porosity or scalp oiliness, and small changes are invisible.
- Talking to your barber or stylistNo study tests how to brief a barber, so the consultation checklist is professional practice, while the health parts (scalp checks, tool hygiene) have small peer-reviewed support.
- The hair growth cycleEvery scalp follicle cycles through growth, shutdown, rest and release on its own clock, which explains normal shedding, seasonal changes, maximum length and how pattern hair loss works.
- Thinning hair, styling and camouflageCuts, fibers, powders, wigs and scalp micropigmentation can hide thinning, but no study compares them, and none of them treats the cause.
- Traction and hairstylesTight, long-worn styles can cause traction alopecia, which reverses if caught early and scars if it is not.
- UV and sun damage to hairSunlight fades colour and weakens hair through free-radical damage, with light, bleached and coloured hair most affected.
- Water temperature and hair washingNobody has studied shower temperature on hair or scalp, so lukewarm water is the sensible choice based on skin data, and cold-rinse shine claims are untested.
- When to see a dermatologistMost gradual thinning is pattern loss you can start treating yourself, but scarring signs, scalp symptoms, patches or sudden shedding should go to a clinician quickly because delay can cost permanent hair.
Conditions Common scalp and hair problems · 19
- Alopecia areataAn autoimmune condition where the immune system attacks growing hair follicles, causing round patches or total hair loss; three oral JAK inhibitors are approved for severe cases but hair usually goes again when treatment stops.
- Anagen effluvium (chemotherapy-induced hair loss)Abrupt loss of actively growing hairs because chemotherapy or radiation shuts down the dividing cells in the hair bulb; hair usually regrows, and scalp cooling is the main way to prevent part of the loss.
- Androgenetic alopecia (male and female pattern hair loss)The most common cause of hair loss is an inherited, slowly progressive shrinking of scalp follicles; it cannot be cured, but finasteride, minoxidil and transplants slow, partly reverse or camouflage it.
- Central centrifugal cicatricial alopecia (CCCA)The most common scarring hair loss in women of African descent, starting at the crown and spreading outward; early diagnosis matters because lost follicles are replaced by scar.
- DandruffDandruff is a common, chronic flaking of the scalp driven by yeast, skin oil and your skin's sensitivity, and an antifungal shampoo controls it well as long as you keep using it.
- Frontal fibrosing alopeciaA scarring hair loss that pulls the front and temple hairline back, often with eyebrow thinning; lost follicles do not return, so treatment aims to stop progression early.
- Hair shaft disordersStructural defects in the hair strand itself, either inherited or caused by repeated stress, that make hair break easily and can look like thinning even though the follicle is healthy.
- Itchy scalpAn itchy scalp has many causes, and the most common is dandruff or seborrheic dermatitis, so check for flakes first and think about allergy or nerve causes if the skin looks normal.
- Lichen planopilarisAn immune-mediated scarring hair loss, mainly on the crown and sides, that destroys follicles permanently; early treatment aims to stop activity because lost hair does not return.
- PCOS and hairPolycystic ovary syndrome can cause female-pattern scalp thinning plus unwanted facial and body hair from excess androgens, but pattern hair loss alone does not prove PCOS.
- Postpartum hair lossMost women shed noticeably more hair in the months after giving birth, as the long growth phase of pregnancy ends and many hairs fall together; it usually peaks around 4 to 5 months and fades by about 8 months.
- Scalp folliculitis and acneScalp bumps are usually mild folliculitis that settles with gentle care, but recurrent, crusting or scarring bumps can be a permanent hair-loss condition that needs a dermatologist.
- Scalp psoriasisScalp psoriasis is an autoimmune skin condition that needs medical treatment, not just a stronger shampoo, and good options exist from topical steroids to biologics.
- Seborrheic dermatitisSeborrheic dermatitis is dandruff with redness and inflammation, and it is controlled rather than cured with antifungal shampoos and, for flares, short-term anti-inflammatory treatment.
- Telogen effluviumA temporary burst of diffuse shedding that starts 2 to 3 months after a physical or emotional shock and usually settles within 6 months once the trigger is gone; it does not cause bald patches.
- Thyroid disease and hairThyroid hormone is needed for normal follicle function, so an under- or overactive thyroid can cause diffuse shedding and brittle hair, but most ordinary hair thinning has a normal thyroid test.
- Tinea capitis (scalp ringworm)A fungal infection of scalp skin and hair shafts that mostly affects children but also adults; it needs oral antifungal medicine, and shampoo alone will not cure it.
- Traction alopeciaHair loss from repeated or constant pulling on the follicle by tight braids, weaves, buns or ponytails; it starts reversible but can become permanent if the tension continues.
- Trichotillomania (hair-pulling disorder)A recognized disorder of repeatedly pulling out your own hair despite trying to stop; behavioural therapy such as habit reversal training is the best-supported treatment.
Procedures Treatments done by professionals · 13
- Botulinum toxin (Botox) for hair lossSmall trials suggest scalp injections of botulinum toxin might raise hair counts a little, but the newest blinded trials found no benefit and it is not approved for hair.
- Electrical, radiofrequency, ultrasound and massage devicesBeyond lasers and microneedling, other hair devices rest on one small maker-linked sham-controlled trial, pilot studies or lab work; most have no controlled hair-growth trial at all.
- Exosomes (extracellular vesicles) for hair lossExosomes are tiny packets released by lab-grown cells that clinics inject or apply to the scalp; animal data look good, human data are small and mostly uncontrolled, and no exosome product is approved in the US.
- Hair cloning and follicle regenerationTrue hair cloning is not available anywhere; the nearest real thing is injecting your own cultured follicle cells, which shows modest, temporary gains in early Japanese trials.
- Hair transplant (FUE, FUT, DHI, beard and brow)A transplant moves balding-resistant follicles from the back and sides of the scalp, or the beard, into thinning areas; most grafts survive, but donor hair is finite and cheap clinics cause real harm.
- Hairline-lowering (forehead-reduction) surgerySurgeons remove a strip of forehead skin at the hairline and pull the scalp forward to lower a naturally high hairline in one operation, mostly for women with a stable hairline.
- Low-level laser therapy (red-light caps, combs and helmets)Red-light lasers and LEDs worn as caps, combs or helmets add a modest amount of hair over sham devices in mostly industry-funded trials.
- Mesotherapy for hair lossMesotherapy means injecting small amounts of a drug or vitamin mix into the scalp skin; evidence is mostly case series and small trials, mixtures are not standardized, and some reports describe the injections themselves causing bald patches.
- Microneedling for hair lossRolling or stamping fine needles into the scalp is a cheap add-on to minoxidil that helped in small trials, but it has not worked on its own and the largest trial found no extra benefit.
- Platelet-rich plasma (PRP) for hair lossYour own blood is spun to concentrate platelets and injected into the scalp; pooled trials show a modest gain, but individual trials conflict and each session is costly.
- Scalp cooling for chemotherapy hair lossCooling the scalp before, during and after chemotherapy keeps roughly half to two-thirds of people from losing more than half their hair, but it works best with taxanes and has no proven use outside chemotherapy.
- Scalp micropigmentation (SMP)Scalp micropigmentation tattoos tiny pigment dots into the scalp to mimic shaved hair or add the look of density; it grows no hair and the evidence is mostly small case series.
- Stem cell and growth factor treatments for hair lossClinics inject fat-derived cells, the fluid those cells grew in, or concentrated growth factors into the scalp; small trials mostly report gains, the best-controlled show little advantage, and none of it is approved for hair.