I'll start by explaining in a simple way how the oil (sebum) appears on the scalp.

Sebum appears due to sebaceous glands under the surface of the skin. These glands produce an oily substance that reaches the skin's surface through the hair follicles.

Having some sebum is good for the skin, but some people are more likely to produce excess sebum.

The hypothesis that I see most refer to is the implication that removing these natural oils (or tallow) with a sulfate shampoo will cause the glands to produce more oil, leading to oily hair.

To understand how this works, we must first understand how sebum production is regulated, in other words, what turns sebum production on and off.

Apparently it is the presence of sebum on the skin's surface that controls sebum production. How is this possible?

We can see here in this article https://link.springer.com/article/10.1007/BF00560397 in which they stripped the skin of its natural oil and then measured the time it took the skin to regain sebum.

This information indicates that the presence of oil on the skin's surface sends a signal to the sebaceous glands to shut down. This signal can be caused by the pressure of the oil in the follicle or by the creation of a chemical signal to the skin. In theory this seems to make sense, right?

The problem here is that there is no way for the skin to detect how much oil it has. The sebum is produced up to a certain amount in the skin and is then stopped by the physical phenomenon of tension surface, so it will end up with the same amount of sebum, whether natural or from an oil.

The amount of sebum that the skin can have will depend on genetic and hormonal factors, etc. - not on the amount of sebum that is placed on the skin (hence the poo does not work in this myth).

That is, even if the hair when washed indicates that in order to produce more sebum, this production will balance when it reaches the necessary amount.

These people say that cleaning the sebum on the scalp will lead the sebaceous glands to compensate for this removal and to produce more sebum. I discovered that this is already known on the internet as "reactive seborrhea" - a myth not supported by any scientific evidence.

In fact, I think I'm going to start by calling these people “activists in the poo”.

http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.533.4687&rep=rep1&type=pdf

According to this article from Journal of the Society of Cosmetic Chemists:

“Several studies have shown that the amount of sebum that appears after the skin is cleaned comes mostly from a reservoir in the pilosebaceous follicle and not from any feedback from stimulation of the sebaceous gland… most anti-dandruff shampoos showed no significant change in the amount in the excretion of sebum during the time of use. This discovery confirms the myth that is often called "reactive seborrhea" which states that sebaceous excretions increase with the frequency of hair washes.”

The study shows a link between excessive oil production and anti-dandruff shampoos that contain selenium sulfide.

https://www.sciencedirect.com/science/article/pii/S0022202X15490633

This study also agrees with everything I have described here - there is no feedback mechanism and that sebum levels are controlled by capillary action and tension surface.

The exception is if there are scalp problems that are drier than normal (or psoriasis, seborrhea, etc.), which in these cases it is necessary to take this into account.

A fact: If the hair is washed too often with products with a very detergent action, the sebum will be constantly removed and the scalp will logically be chronically dry.

People, like us curly, who use finishing products, creams, gels, etc., will eventually need to wash their hair with a shampoo with surfactants that can disperse these oils and dirt well, as these products often include small amounts of insoluble compounds that may accumulate in the hair over time.

However, this study says that the scalp will not make up for being too dry if too much shampoo is used. It is one of the myths with pseudo science that are said on the internet so it is because it is true.

Depending on the type of hair and how oily it is, you can even benefit from not washing it too often - it could be an experiment to do. But stop using shampoo just because someone said it makes your hair look more oily - this just isn't true.

If there are sebaceous glands that are too active it is normal to get more oily skin and hair. But this oiliness does not come from the shampoo.

The problem here is that there are people who are “hair extremists” - where there is only one way to care for the hair and everything else causes the hair to fall out.

It is also easy to forget that you are not only treating your hair, but also your scalp. The scalp is skin. You don't see these people, who say that everyone needs to wash their hair in a certain way, that this should be done the same on the skin. Some of us use only a moisturizer while others have a 15-step routine: it's exactly the same as with the scalp.

Try to do the most gentle thing for your scalp. For curly hair, they may decide to wash their hair less often and with milder shampoos. If it is not working, insert a more clarifying shampoo in the routine to be used more sporadically.

However, be careful with this inconsistent wash, as in some cases it can lead to problems in the scalp of sebum accumulation.

I also want to mention that it is possible to have residue accumulation even when washing with low poo shampoos, as some may not be strong enough to remove some ingredients from the hair.

As I mentioned here before, this accumulation of residues can lead to scalp problems and before thinking that the problem is in the routine, I just suggested adding a sporadic wash with a sulfate shampoo.

One of the things I'm going to introduce into my routine is going to be a clarifying shampoo.

I'll use: co wash + low alternating poo + clarifying shampoo 1x per month

Lately I feel that my hair is not defining as it should, probably because I have not washed it with a stronger shampoo for a long time (before I went to the hairdresser and did this washing there, now it is difficult so I have to do it myself) .