There is a whole world of nonsense out there in the marketing of haircare products to women. There are wild claims, like “unlocks the power of nature to give you 10X stronger hair”. There is all the jargon that means heaven knows what, like “our patented Bio-Ceramide Complex” or “natural protein fortifies hair for touchable softness” (well, if the softness is touchable, I better get a bottle now!). There are all those ingredients that must do something amazing, because you’ve never heard of them before, à la “argan oil from Morocco”.

Hollywood stars who have an army of stylists to get them looking just right rabbit on about products you are fairly sure they’ve never tossed into a shopping trolley. And of course, there are those pictures of models with tresses so long, shiny and digitally enhanced that it looks more like magical pony hair.

I think this haircare-ad spoof The Chaser team did, back when they were doing the show CNNN, is just gold. A woman’s dull, lifeless hair is “letting her family down” but after using “Esteem” shampoo her hair becomes “full of adjectives”:

A lot of teens spend a lot of hours angsting over their hair, as teens always have. How to wear it, how to cut it, how to make it straight or curly or thicker or thinner, how to get parents to agree to a hairstyle — you might remember going through all this yourself. And then there is the eternal greasy hair dilemma. The same hormone change in puberty that is responsible for the extra sebum (oil) production that leads to pimples is responsible for the oily scalp and hair that many girls feel self-conscious or even ashamed about.

With all these ads promising astonishing transformations, it’s no wonder that many girls (and women) go through a tonne of hair product and a mountain of disappointment looking for the magic bottle that will give them the “hair” they see on ads. I say “hair” because no one has hair like that, even the people in the ads. They have gone through hours of styling, are lit by state-of-the-art studio lighting and are then digitally enhanced. Ken Paves, who styles celebrities such as Eva Longoria and Jessica Simpson for hair ads, was quoted as saying, “It takes four hours of prep for one hair shot.”

To cut through all this trickery, I went looking to find out, realistically, how often it’s a good idea to wash hair and what to look for in products. And you know, for all the people in lab coats with molecular diagrams swirling around in the background of haircare ads, it turns out that there really aren’t many established scientific facts about hair washing. According to How Stuff Works, there is disagreement among medical experts who specialise in hair, skin and scalp about how often to wash hair — or even whether it’s a good idea to wash it at all!

One thing that seems clear, though, is that you probably don’t need to spend a lot of money on shampoo. They give a great explanation of what shampoo actually is: it’s about half water, with a mild detergent such as sodium laureth sulfate, plus coconut oil byproducts that don’t do anything for your hair but give the shampoo a desirable texture. Check out how quickly and easily a chemist can knock up a batch:

They recommend using a cheap, basic shampoo and saving your money to spend on conditioner.

I was surprised to find out how new the idea of regular shampooing is.

Back in the 1950s, it was common for women to have their hair washed and styled once a week at the hairdresser . . . Around the turn of the 20th century, women tended to go for about a month between salon visits. — How Stuff Works

After ABC radio presenter Richard Glover interviewed Times journalist Matthew Parris, who said he hadn’t washed his hair for 10 years, he challenged his readers to do the same for 6 weeks. Five hundred people took up the challenge, and 86 per cent of them said their hair was either better or the same.

I can’t see many teen girls wanting to try that out — me neither! So this is the advice I gleaned from Paula Begoun, “The Cosmetics Cop”, who devotes her time to debunking the outlandish promises made by the cosmetics industry: “Even washing hair on a regular basis . . . causes irreversible damage. There are ways to mitigate the damage: wash hair less frequently, condition the hair, and use protective styling products and conditioners . . . don’t over-strip hair by overdoing hair dyes . . . and use blow dryers and flat irons intermittently and carefully.” She recommends that you spend more time washing and massaging the scalp, to increase circulation, than the ends.

Some girls are embarrassed because they break out in acne around their hairline, and Begoun says that can be because some of the ingredients in shampoos and conditioners “are designed to stick to hair, which means they can also ‘stick’ to skin, too, and potentially clog pores”. She suggests rinsing well, using a gentle body and face cleanser, using only just enough conditioner, and going light on styling products.

And all those products that are designed to combat limp hair? Well, products themselves might be causing the limp hair in the first place. She says it’s best to use a shampoo with few or no conditioning agents and apply conditioner only where you need it, “not necessarily all over or near the roots and scalp”.