I don’t think I’m alone in planning my week according to when I’m washing my hair. 

After all, I’ve got pretty long hair that’s not thick but is definitely plentiful ― the sort of thing that makes beleaguered hairdressers say “wow, that’s a lot of hair!” while blow-drying it. 

So, I’m always happy to hear I need to wash or dry it less often. I learned about the idea of “oil training” ― only washing your hair once or twice a week, so it “learned” to get less greasy ― a couple of years ago, when it went viral on social media. 

Dr Karan Rajan, a surgeon, author, and lecturer, has sad news, however. 

Stitching a video of another TikToker who claimed that not washing your hair every day will cause hair loss, the doctor said: “I’m ashamed to admit that I used to believe this, and you probably did too.”

What’s “this”?

“There is no evidence linking regular hair washing to hair loss,” he explained. 

That means a core belief behind the low-wash theory ― that washing your hair whenever it feels greasy strips it of oils it needs to stay healthy ― is not scientifically backed. 

“In fact scalp hygiene may actually promote healthy hair growth, because it can stop the buildup of excess sebum (oil) which can clog the hair follicles,” he added.

Shampooing also helps to “wash away dirt and pollutants which can contribute to scalp inflammation,” he continued.

Speaking to health information site Healthline, Sam Carpenter, global educator at haircare company EIDEAL said that both an inflamed scalp and a buildup of sebum can lead to an increased risk of hair loss. 

“For me, the biggest issue with not washing hair regularly is that you could be at risk of developing seborrheic dermatitis, a common skin condition that primarily affects the scalp and is characterized by red, itchy, and inflamed skin,” Dr Fariha Anwar, an aesthetic doctor at Euromed Clinic Dubai, also told the publication. 

This has also been associated with hair loss. 

So, do I have to wash my hair every single day?

All hair types are different, so no, not if it doesn’t need it. 

The American Academy of Dermatology Association says; “If you have straight hair and an oily scalp, you may want to shampoo every day. If your hair is dry, textured, curly, or thick, shampoo when needed — at least once every 2 to 3 weeks as needed.” 

Noticing limp, greasy, flaky, or itchy hair can be a sign you need to shampoo it.

Still, the lesson stands ― though Dr Karan Rajan points out that using dyes, harsh products, and excessive heat on your hair can weaken it over time, there’s no real medical heft to the “oil training” trend. 

His comments are backed up by a 2021 study whose results researchers hoped would rid us of “unfounded concerns that high shampoo wash frequency is detrimental in any way.”