How often should we wash our hair?

The internet is full of opinions on the ideal interval between hair washes, from daily to weekly to not at all.

The latest word on the topic comes from the Cleveland Clinic in the US and backs washing your locks daily.

Are you washing your hair enough?

Sunday Morning

Dermatologist Dr Adrian Seine weighed in on the research on Sunday Morning, telling host Jim Mora that the findings by the Cleveland Clinic and others were backed by evidence and had been subject to peer review.

"I think it is pretty spot on, really... And washing five or six times a week seems to be optimal for most people who are living in a modern urban environment where there's a lot of sweat, pollution and oil."

Not everyone is the same though: "It also comes down to the right frequency to keep your specific scalp clean."

He countered the "common misconception" that washing too often with shampoo damaged the hair or made the scalp greasy.

"Your scalp doesn't really have any eyes or feedback loop. It has no idea when you've washed it. So it doesn't really compensate by producing extra oil. And actually, whilst overwashing might wash out the hair strand, you're not looking at drying out the oil production.

"It's important to separate those two things. You're talking about the hair and you're talking about the scalp. And when we're talking about using shampoo, you're looking specifically at washing the scalp rather than the hair itself.

"The idea behind shampoo is that you're going to part your hair and you're going to rub it onto your scalp itself. You don't want to go piling your hair up like a loaf on top of your head and rub it all together. You actually want to part the hair, get the shampoo on the scalp, reduce that oil production, that sebum that your body is producing, to break it down.

"And then when you wash your hair, simply that act of the shampoo washing through your hair is enough for the rest of the hair in terms of a wash when you're doing it regularly."

Conversely, conditioner was more for the hair than the scalp.

"So conditioner is being applied ... from about an inch off the scalp surface along the length of the hair to rehydrate the hair and to seal it off and to improve its strength."

Caution on shampoo alternatives

Quizzed on shampoo alternatives such as apple cider vinegar or tea tree oil, Seine sounded a note of caution.

"In the right settings, you can use apple cider vinegar ... But when you're looking from a point of view of your scalp, it may alter the pH temporarily but it doesn't really do anything to lift off that buildup of the oils and those lipids that the dandruff-causing yeast is feeding on.

"When it comes to tea tree oil, it's not knowing the right percentage that's going to be available. And whilst it does have good antifungal properties, the concern from a dermatologist perspective is that you could cause more problems. It's not uncommon that with these natural botanical products like tea tree oil that you can start causing issues known as an allergic contact dermatitis, an eczema-like eruption of the skin because the body's reacting to that natural tea tree oil."

Never washing your hair got the thumbs-down.

"You only have to look at someone who has dreadlocks to understand that if you don't wash your hair, your hair will start sticking itself together. It's the same as any other bit of skin on your body. If you don't wash the rest of your skin on your body for weeks, it's not going to become naturally luxuriant and greasy and shiny and lovely. It's going to get irritated, inflamed and smelly, and the scalp is no different.

"Your hair does not self-clean and the sebum that your body produces simply accumulates and oxidizes and that triggers inflammation and promotes the growth of that yeast malassezia that's responsible for causing dandruff."

Coffee grounds 'messy and abrasive'

Also ruled out was rubbing coffee grounds into your scalp to promote hair growth.

"Personally, I enjoy drinking it more than I enjoy rubbing it on my head. However, what I would say is that we know that topical caffeine - so not coffee but topical caffeine - can stimulate hair follicles to grow. And there are quite good products out there that have done research and got the right concentration.

"However, if you're looking at trying to do the kitchen hack or the at-home DIY, rubbing coffee grounds in your head is probably going to be more messy and abrasive. And really, we don't know how much caffeine's in there, if any, because you've probably drunk it all by that stage. They also haven't been packaged in the right way to effectively penetrate down the root of the follicle. So the caffeine's not going to get where it needs to go."

On the notion that hair dryers caused damage, Seine was more forgiving.

"Everyone used to think that hair dryers were going to damage your hair and you should let it air-dry. But ... the truth lies in between those two," with prolonged air-drying also causing damage.

"When the hair stays wet for hours while it's drying, then that sort of cellular matrix in the membranes, they swell up with water and it causes fatigue and fragility in the hair.

"So actually what you should be doing is let the hair air-dry about 70 or 80 percent of the way there and then finish it off with a low-heat hair dryer, keeping it about 15 centimetres or so off the scalp to prevent that direct heat damage."