It’s a question that has divided social media and hair stylists for years: how often should you wash your hair?
While some people swear they need a daily rinse to feel grease–free, many others insist on using shampoo as little as possible.
Now, scientists have finally settled the debated.
And their answer might be disappointing for anyone who hates washing their locks.
According to the experts, your hair is usually happiest and healthiest when it is washed five or six times per week.
In one trial, researchers found that washing almost every day led to the best scalp condition and the most ‘great hair days’.
While researchers caution that the exact frequency will depend on hair type, they suggest that worries about ‘overwashing’ are unfounded.
Dr Shilpi Khetarpal, board–certified dermatologist at the Cleveland Clinic, warns: ‘When the hair and scalp are not cleaned frequently enough you can get an overgrowth of bacteria and yeast.’
The question of how often you should wash your hair has divided the internet, but now scientists have revealed that you should be washing your hair five to six times a week
Increased frequency of hair washing led directly to better hair, with participants in a large trial reporting a higher number of ‘great hair days’ per week
The debate over how often you should wash your hair has raged for years on social media, with many people remaining convinced their method is the best.
On one hand, it is a commonly held belief that washing with shampoo too frequently can damage the hair or lead to the scalp becoming greasier over time.
In a post on Reddit, one social media user wrote: ‘If I rinse my hair after exercise I can go a week straight without shampooing it and it looks fine.’
‘My hair is thick and curly and it is much better if I don’t use shampoo every day; sometimes I just get it wet and put in conditioner,’ added another.
Another commenter wrote: ‘I legitimately shampoo my hair once or twice a month, if even that.’
Likewise, some social media users say they have sworn off using shampoo altogether and have ‘trained’ their hair to need less frequent cleaning.
However, many people still say that waiting more than a day or two between washes leaves them feeling greasy and unclean.
‘My hair must be washed with shampoo every other day or it gets slimy and disgusting,’ one commenter wrote.
While some people swear they need a daily rinse to feel grease–free, many people insist on using shampoo as little as possible to avoid damaging their locks
Another said that their hair felt ‘so soft and beautiful, hydrated’ when they washed their hair with shampoo every single day.
Research suggests that advocates of more frequent washing are in the right.
A study conducted by Procter & Gamble recruited over 1,500 men and women to take part in a trial testing the effects of different hair washing schedules.
The participants either washed their hair once a week, twice a week, three to four times a week, or five to six times a week.
Afterwards, they rated how healthy their hair felt as well as how many ‘great hair days’ they had in a week.
The researchers found that the more frequently people washed their hair, the better they felt it looked.
People who washed their hair almost every day had the lowest levels of self–reported itchiness, dandruff, and scalp irritation, and the highest number of great hair days.
Some social media users even claimed to wash their hair ‘once or twice a month’ without feeling greasy
This is because going longer periods without washing your hair leads to a buildup of an oily substance called sebum.
Sebum normally helps hair retain its moisture and keeps the scalp healthy, but excess amounts can lead to issues.
Dr Khetarpal says that this oily substance becomes the food for colonies of bacteria and yeast that live on your scalp.
‘Bacterial overgrowth can lead to acne–like bumps in the scalp called folliculitis. Yeast build–up can present as dandruff or seborrheic dermatitis, where there is flaking, itching and redness of the scalp.’
To make matters worse, if sebum sits on the scalp for too long it starts to chemically alter.
This releases chemicals called free fatty acids and oxidised lipids, which are known to be irritating to the skin.
That’s why using shampoo to wash the scalp more frequently helps to keep the hair cleaner and healthier for longer.
While the researchers caution that the ideal washing schedule depends on your hair type, more recent studies suggest that this might not be the case.
A study found that washing every other day led to an increase in hair cleanliness and decreased itchiness, dryness, and dandruff – regardless of hair type
In the past, it has typically been suggested that thick, curly hair should be washed less frequently than thin, straight hair.
However, a study conducted in 2023 found that all types of hair actually benefited from more frequent washing.
When participants washed their hair on alternating days, they saw improvements in cleanliness, itchiness, dryness and dandruff.
This was even true for ‘type–4’ coily or Afro–textured hair, which people are often advised to avoid washing frequently.
Importantly, the researchers noted that those participants who washed their hair the least frequently before the trial started saw the biggest improvements.
These findings run contrary to the belief that more frequent shampoo use will damage hair by stripping away healthy oils, leading to drier strands.
Both studies found that more frequent washing did not produce any additional hair damage.
In fact, the Procter & Gamble study actually found that participants’ hair retained more moisture than hair that was washed less often.
The less people washed their hair before changing to cleaning more frequently, the bigger the improvements people saw. This suggests that more frequent shampooing is significantly better for your hair
Likewise, participants who shampooed daily showed no differences in levels of internal lipids, which are beneficial for hair, compared to a baseline of washing once per week.
However, experts do caution that you still need to use some care not to damage your hair with more frequent washing.
Dr Antonella Tosti, a dermatologist from the University of Miami, told the Daily Mail: ‘What is important to wash frequently is the scalp, not the hair fibre itself.
‘Excessive washing can damage the hair fibre, and it is important to protect the hair shaft with conditioners.’
