Topic
Hair myths, checked
Twenty-five popular hair beliefs checked against the evidence, from shaving to biotin to baldness genes.
"Unproven" below means we found no controlled human data; it does not mean the opposite is proven.
Key takeaways
- Most hair rules are half-true: they describe a real mechanism but are wrongly applied. Wet hair is fragile, yet air-drying is not the safest option.
- The costly myths push people to buy supplements instead of proven treatments for pattern hair loss.
- Several popular rules (shaving, brush strokes, hats) are false or unsupported and can be dropped at no cost.
- Where a sibling page covers the details, it is linked.
The myths
- Shaving or cutting makes hair grow back thicker or faster. False. The classic test, a 1970 paper on shaving and hair growth, is described in secondary summaries as finding no difference in hair weight, width or growth rate. Lynfield 1970 A blunt cut tip and unlightened new hair make stubble look coarser.
- Washing every day causes hair loss. False. Hairs in the drain were already shedding. See washing frequency. A 2002 nutrition review notes that many patients cut back on shampooing out of fear, which worsened scalp scaling. Rushton 2002
- Washing more makes your scalp oilier. Not supported. Sebum is hormone-driven. See washing frequency and sebum and scalp types.
- Washing daily is best for everyone. Oversimplified. The pro-daily-washing study was manufacturer-funded with unbalanced groups, and curly and coily hair do fine on lower frequency.
- Air-drying is the gentlest way to dry hair. Partly false. Tests found no cuticle damage from air drying, but heat damage rose with temperature. See hair drying.
- Rubbing hair with a towel is fine. False. The American Academy of Dermatology lists rubbing hair dry among habits that damage it. See hair drying.
- Brushing 100 strokes a day makes hair healthy. False. The same body calls it a myth. See brushing and detangling.
- Silk pillowcases prevent hair loss. Unproven. No human trial; a plausible friction benefit for tangles. See sleep and hair.
- Hats and helmets cause baldness. Unproven for pattern loss. Tight headwear or styles can cause traction damage; see traction and hairstyles.
- Baldness comes only from your mother's side. False. Pattern hair loss is polygenic: genome-wide studies have found more than 380 associated loci. Liu 2025 The androgen receptor gene sits on the X chromosome, which fed the myth, but it is one contributor among many. Heilmann-Heimbach 2020
- High testosterone causes baldness. Oversimplified. Loss is hormone-dependent but depends on follicle sensitivity, not simply on having more hormone. Heilmann-Heimbach 2020 See DHT and pattern hair loss.
- Only men go bald. False. Pattern loss affects women, mostly after menopause. Liu 2025 Vitamin D studies include female pattern hair loss. Yongpisarn 2024
- Lifting weights makes you go bald. Unproven. See exercise and hair.
- Stress turns hair gray overnight. Not supported in humans. A 2021 mouse study shows chronic stress hormones keep hair stem cells dormant. Choi 2021 See gray hair.
- Smoking or alcohol cause baldness. Associated, not proven. See smoking, alcohol and hair.
- Everyone should take biotin for hair. False. Benefit is shown only in deficiency, and biotin can distort blood tests. See biotin.
- Hair vitamins and gummies regrow hair. Partly supported for some branded products in small, industry-linked trials. See hair supplement blends.
- Collagen, keratin or marine-protein supplements rebuild hair. Weak. See collagen peptides, keratin supplements and marine protein supplements.
- More vitamins always help. False. Excess selenium and vitamin A can cause hair loss. See selenium and vitamin A.
- Crash dieting is harmless to hair. False. Rapid weight loss triggers shedding months later. See diet and hair.
- Eating more protein makes hair grow faster. Only if you were short.
- Vegans always lose hair. No hair data; the risk is iron, zinc and B12 gaps that can be tested.
- Scalp massage regrows hair. Unproven (one 9-man study). See scalp massage.
- Dandruff means a dry scalp. Usually false. Flaking is most often a yeast- and sebum-related inflammatory response treated with antifungal shampoos. See dandruff.
- Wigs, weaves and braids always cause loss. Only when tight, heavy or worn too long. See traction and hairstyles and traction alopecia.
Bottom line
Skip rituals with no evidence (100 strokes, expecting shaving to thicken hair), fix measured deficiencies, avoid megadoses, and use proven treatments for pattern loss (androgenetic alopecia). Discuss with a doctor.
Studies 6
Lynfield YL et al. Shaving and hair growth. 1970
Result: Classic test of shaving and hair growth, described in secondary summaries as finding no difference in hair weight, width or growth rate.
Read the study ↗Rushton DH et al. Nutritional factors and hair loss. 2002
Result: Recommends ferritin around 70 micrograms/L for increased shedding, reports lysine plus iron responses, and warns that excess supplements can cause hair loss.
Read the study ↗Liu Y et al. Androgenetic alopecia. Nat Rev Dis Primers. 2025
Tested: review
Result: More than 380 loci including androgen and WNT pathway genes; the molecular basis of female AGA remains undetermined; occipital follicles are androgen-resistant.
Read the study ↗Heilmann-Heimbach S et al. Hormonal regulation in male androgenetic alopecia-Sex hormones and beyond: Evidence from recent genetic studies. 2020
Result: Pattern hair loss is highly heritable and hormone-dependent, driven by follicle sensitivity.
Read the study ↗Yongpisarn T et al. Vitamin D deficiency in non-scarring and scarring alopecias: a systematic review and meta-analysis. 2024
Result: Deficiency in about 47-54% of patients; lower levels than controls only in alopecia areata and female pattern loss.
Read the study ↗Choi S et al. Corticosterone inhibits GAS6 to govern hair follicle stem-cell quiescence. 2021
Result: Chronic stress raised corticosterone, suppressed Gas6 from the dermal papilla and kept follicle stem cells dormant; restoring Gas6 reversed it.
Read the study ↗Related
- 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.
- 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.
- Brushing and detanglingMost combing damage comes from tangles, so conditioner and the right technique cut breakage more than the choice of brush.
- 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.
- Exercise and hairThere is no human evidence that exercise causes or prevents pattern hair loss; under-fuelling is the bigger risk.
- Smoking, alcohol and hairSmoking goes with early graying and probably earlier pattern loss, but the evidence is observational and mixed.
- Diet and hairCrash diets and rapid weight loss cause shedding, ordinary diets rarely do, and testing beats guessing before you buy supplements.
- Scalp massageFree and harmless, but the only human evidence is a nine-man study without a control group.
- Traction and hairstylesTight, long-worn styles can cause traction alopecia, which reverses if caught early and scars if it is not.
- BiotinA B vitamin that restores hair only in the rare people who are deficient, and that can scramble thyroid and heart blood tests at the doses sold for hair.
- Hair supplement blends (Nutrafol, Viviscal and similar)Branded multi-ingredient hair vitamins that beat placebo in small, mostly company-linked trials.
- SeleniumAn essential mineral with no proof that supplements regrow hair, and a well-known cause of hair loss in excess.
- Vitamin AToo much preformed vitamin A can make hair fall out, so extra vitamin A in a hair supplement is more likely to harm than help.
- 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.
- 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.
- 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.