how often to shampoo
As you likely know, the scalp has sebacious glands that constantly produce its own sebum (a waxy ester sometimes referred to as oil) that when hair is left unwashed coats the hair for approximately 4-6" down the length from the roots. This natural production of sebum has much to do with age really meaning hormones and to an extent, a response to frequency (or not) of washing.
It is understood that if one washes daily thereby stripping the hair of its sebum, this sebum produces a little faster to replace what’s missing from the scalp skin and the hair. In my opinion, sebum production is not so much something our bodies do to benefit our hair — that just happens to be an aside — rather, it is intended to keep our scalp skin healthy.
However, it’s possible to go too far in the nonwashing. At a certain point, sebum will break down. On our skin (scalp skin included) is ever present bacteria that at a certain point begins to break down sebum. This bacteria can get into hair follicles/roots and cause early release of hair. An indicator of sebum buildup gone too far is a rather pungent odor, and of course, the hair is rather cake-y in appearance on the top of the head.
Locating the balance point between allowing some sebum buildup to occur and the next hair washing. Obviously, one does not want to encourage early release of healthy hairs.
It is also possible, in the process of allowing a longer duration between hair washings to also get clogged hair follicles/roots from sebum buildup. The hair follicles/roots are not unlike the rest of our skin which does have little hairs sticking out all over our bodies (some thicker and easily visible; others are finer and not as easily seen). All skin can get a pimple or an ingrown hair and often these are due to a clogged pore from dirt, grime, and yes, even our own sebum on our scalp.
Hair washing is, in my opinion, more about cleansing the scalp than washing the hair. Notice that hair length does not require the same cleansing schedule as the scalp hair might, or the scalp itself might. This is why some of us scalp wash: to get at the scalp and the hair on top of the head more frequently while leaving the length alone.
In my opinion, being able to grow beautiful hair has much to do with the health of the skin of the scalp since hair itself is dead yet the skin is a very alive organism as are the roots/follicles under the surface of the scalp’s skin.
So, typically, in scalp washing, the first wash is to get the grime off of the scalp hair–the hair. The second wash is to create a slightly larger lather (now that the grime/buildup of sebum is removed), and this lather should be massaged into the scalp skin. Some find they need more than 2 shampoo’s to adequately cleanse the scalp and the hair on the top of the head.
Yes, the scalp does to a degree regulate its flow according to frequency of washing. (For those who do indeed need frequent washings, using a gentler shampoo is required.) Follicles/roots can indeed become clogged from not washing, and although the likelihood increases with less frequent washings, it can occur with frequent washings, too! Not unlike acne. We wash our faces daily yet acne happens even so.
The key in washing the scalp’s skin is massaging the lather into this skin.
With this new consideration of paying attention to work the lather into the scalp’s skin, it may be a while before you notice any increase in hair’s density (hairs per square inch on the head)….but keep aiming to cleanse the scalp and in time you should definitely notice some increase in new growth.
Do not use "clarifying" shampoo at every single washing. Use it when you need it. You might find occasion to use it repetitively two times in a row, but it should not be used as your shampoo choice on a regular basis if it’s a "clarifying" shampoo. These shampoos strip the hair of all oils and leave the hair quite dry. When this occurs, you must replace as immediately as possible what has been removed.
Allow your sebum to manage the top hair down to around the earlobes (give or take). Wash hair, I’d say, approximately every 3 days if you can go that long, depending on your sebum production. (Of course you can scalp wash). Use oil in your hair length to coat the hair with a protective layer that imparts a pleasant shine and supple softness.