Deep Conditioning: Everything You Need To Know

This is everything you need to know from the last deep conditioning series

1. Adsorption

Most ingredients in hair conditioner attach to the surface of hair - aDsorb - more details here
-surfactants eg behentrimonium chloride/methosulfate
-emollients e.g cetyl alcohol
-some oils e.g mineral oil, sunflower oil, dimethicone, aminosilicones e.g bisaminopropyldimethicone, amodimethicone

2. Penetration into Hair

Some ingredients in hair conditioner can penetrate into natural hair:
-hydrolysed wheat protein
-coconut oil
-cetrimonium bromide

Hair that is damaged or bleached allows more into hair- more details here

3.  Do you need deep conditioning? Is your natural hair considered as damaged?

You should consider your hair as damaged (even if it is not bleached or colour treated) if it has a high potential to be damaged . For example, it breaks easily, requires very gentle handling, has mid shaft splits or split ends regularly.

4. Deep condition on dry hair, wet hair, before or after shampoo?

Some people like to use a water based deep conditioner before shampooing while others prefer using the shampoo first before deep conditioning. Scientifically, a water based conditioner will work better after a shampoo and rinse. More details here

5. Deep conditioning time and temperature

For maximum effect, 20-30 minutes at 35°C is ideal for a water based conditioner. More details here

6. How to heat up your conditioner before using it.

The Natural Haven water bath method - More details here

7. Over conditioned hair: Do you like leaving conditioner on for hours at a time/ overnight?

Some naturals like the feeling of over conditioned hair - More details here


  1. Thank you for explaining things so thoroughly in your posts! I'm learning a lot.

  2. Hi Jc, thanks so much for the research and writing that you do to help us naturals better understand our hair! I really appreciate knowing the science behind our hair care.

    There is one item in this article that I have a hard time agreeing with, based on my personal experience. It's the assertion that overnight conditioning --> over-conditioned hair --> weaker hair (according to the article you linked). I have noticed that since I have begun deep conditioning overnight on DRY hair (never wet!), I have been able to maintain the level of moisture in my hair for days at a time. I used to have to re-moisturize my hair every night between co-washes so that my hair would not get dry, stiff and tangled. Now, I rarely ever need to re-moisturize between co-washes. I don't have to do any sort of nighttime prep or add anything at all to my hair for days at a time.

    I also use protein whenever I co-wash (my fine hair has always loved protein), and I believe that I am maintaining good levels of protein and moisture in my hair without have to goop in product after product, night after night.

    My hair is flourishing, and I am drastically cutting down my dependence on various hair products. I see dry overnight conditioning as using a super-effective moisturizer that you merely use one night a week, not every night or every other night, like traditional moisturizers are used.

    I just wanted to add my two cents about deep conditioning because naturals, including myself, really trust the advice and scientific explanations that you give. I know that you cited the nail experiment as evidence that > 15 min of exposure to water --> weakened nail keratin, but I do not see the direct translation to hair. We put water in our hair constantly, as water is the main ingredient in the majority of natural products that we use. That is the true definition of a moisturizer: water as the first ingredient. And we are constantly looking for sealers, such as shea butter, coconut or castor oil to seal in that moisture (water) for as long as possible. So I hesitate to believe that the presence of water for > 15 min automatically leads to weakened hair keratin. Maybe the amount of water would need to be taken into account? The amount of water found in a moisturizing or deep conditioning product is a lot different than a full head soaked in water. Maybe it's worthwhile citing that difference, and maybe that's where the difference between wet and dry deep conditioning come in.

    Thanks, Jc!

    1. Thanks for the comment Ashley. I do think that everyone has to follow what they find works for them, so if overnight conditioning works for you, I would say keep it in your routine.

      However, for scientific accuracy, I always have to report based on evidence, so knowing what I know, I would be lying to this audience if I said that overnight conditioning is perfectly fine and I have seen no reason as to why it might be harmful.

      To answer some of your questions
      1. How is keratin in nails related to keratin in hair
      The keratin in nails is actually more similar to the keratin in hair than it is to keratin in skin. Hair and nails have a form of keratin referred to as 'hard keratin' while skin has a form known as 'soft keratin'.

      2. How much water is in a conditioner
      I agree with you in part that a hair conditioner will contain less water than soaking your hair in 100% pure water, however water based hair conditioners are normally around 70-90% water so that is still a pretty high water content. Yes the oils, surfactants etc help to 'buffer' this water content but the product as you know is predominantly made up of water.

      3. Why use a conditioner for hours?
      I have never seen any water based hair conditioner which would recommend leaving the product on for hours at a time (Anyone who has, feel free to correct me, I would definitely like to see it and even write to the manufacturer!). Most will recommend a time level between 5 and 20 minutes. Hair conditioners are designed to work within this time and when you move to an 8 hour stint or more, this in my view on the basis of scientific evidence is likely to create overconditioned hair.

      4. Does greater than 15 min of water/waterbased conditioner lead to weakened hair?
      Your hair will always be weaker when fully wet. This is just a fact. The study I quoted on nails was trying to find a reason why repeatedly soaking nails in water leads to weaker nails. This is something that most of us will know simply by observation. There are two factors involved - soaking for longer than 15 minutes and secondly, repeating this process often. If you have ever had to have your nails in water for a long time you will notice that they will be extremely soft, they will lose their whiteness at the tip and become transparent/translucent. They will be very flexible and if you continuously bend them when they finally dry out and harden up again, you will be able to see the bend where your flexed them. This is because the keratin was weak immediately after the long soak and handled incorrectly you get cracking in your nails (even if you could not see it in the soaked state).

      The science is saying that if you happen to have soaked a hard keratin in protein in water for a long time, be careful with handling it afterwards.

      I do have to transfer this lesson to hair to say to people like yourself who like overnight deep conditioning that although your hair is softer and has excellent flexibility, bear in mind that it will be quite weak. Handle it with great care so as not to create that crack (i.e do not overcomb or overbrush it, do not overstretch it).

    2. Thanks for the explanation, Jc!

      I still find it hard to see how dry deep conditioning overnight is any worse than using a moisturizer nightly, such as Shea Moisture, as so many naturals do. Even if a deep conditioner is 70-90% water, I'm only using a few quarter-sized amounts. My hair is totally dry in the morning. My hair would be wetter if I was spritzing it, which many naturals do do every night (I am not one of them, as I don't like going to bed with wet hair). We in the natural world are encouraged to use moisturizers often (which are also 70-90% water). Does this mean that naturals should stop applying moisturizers nightly, since the water they contain are damaging to the hair keratin? Should the only time we ever expose our hair to any type of water or product be on wash day? I don't see deep conditioners containing any more water than any other moisturizer or leave-in out there on the market, so according to the science that you have cited, does this mean naturals should stop using leave-ins and moisturizers, except on wash day? Many naturals would certainly have to change their regimens, if this were the case, as so many articles for us cite daily moisturizing (i.e., adding water-based products to the hair regularly) as one of the basic tenets of natural hair care and general maintenance. Would love to hear your thoughts around this.

      I doubt that what you are trying to say is that applying moisturizers to our hair throughout the week is damaging or weakening to our keratin, so again, I would like to see an explanation of the difference between applying deep conditioner to dry hair overnight (supposedly weakening) and applying moisturizers to dry hair nightly (a part of many naturals' regimens).

      To clarify, I would absolutely agree with everything you are saying... if we were talking about wet deep conditioning overnight. I, too, agree that that would be overkill and would result in weaker hair keratin. Wet, soggy hair cannot be strong hair. Yet, there is a big difference between applying a deep conditioner to wet or to dry hair overnight, and I would be interested in the research around that. I just find it very hard to believe that the few fingerfuls of water in my deep conditioner, when applied to dry hair, are really wrecking havoc on my strands. I have been finding the opposite to be true. My hair is not any weaker than usual, and I have actually been finding detangling to be easier than normal, with the loss of less hair, which should not be happening if my hair really is weaker. I am also using way less product than I used to, since I no longer have to re-moisturize my hair nightly, which means my hair is being exposed to water-based products less frequently than before.

      I've written a lot, as usual (sorry! I am just so fascinated), but I guess my main questions are such:

      1. Would the water content in a deep condition affect our hair keratin differently than the water content in a daily moisturizer (such as Shea Moisture Curl Enhancing Smoothie, Oyin Hair Dew, or any other widely used moisturizer)? If so, how and why?; and
      2. Does deep conditioning overnight on dry hair have the same weakening effects as deep conditioning overnight on wet hair?

      Thanks! Would love to hear some discussion around those points.

    3. One more question: I loved your example of the nail keratin study. Yes, we all have observed that if we take a long shower, our nails become more bendable and easier to split or break. However, that effect is only temporary. By the time our nails are dry, they seem to have retained their original strength. If this wasn't the case, every time we showered, washed the dishes or went swimming would be death to our nails, and no one on Earth would have any anymore!

      So, my question is: just as nail keratin seems to be weakened when wet for a long time but regains its strength once dry, does hair keratin act in the same manner? Overexposure to water weakens the hair keratin, but does the keratin regain its strength once dry, as do nails? This question is important, because instead of making the blanket statement that deep conditioning overnight --> weakened, over-moisturized hair, maybe the statement would look more like: deep conditioning overnight --> temporarily weakened hair, which regains its original strength once dry.

      Thanks, Jc! I love that you are a scientist and can answer these questions for the rest of us.

    4. Overnight deep conditioning means applying a conditioner to hair, covering it with a plastic cap, sleeping and then washing off the conditioner in the morning. This is what I class as overnight deep conditioning.

      What you are doing is what I class as using a conditioner as a moisturiser. This is not what I would call deep conditioning at all. You are just using it as a leave in from your description. I have already done a blog about that -

      In regards to your second question, I did already answer it in the previous article - see the last paragraph (

    5. Nope. I'm not using it as a leave-in, as I rinse it out the next day and co-wash, detangle as usual. I am applying it to my hair, covering it with my bonnet (not a plastic cap), and then washing it off in the morning. Why would this not be deep conditioning?

    6. If you are saying your hair is dry in the morning that appears to me that the conditioner has dried onto your hair and that is what I would expect from a leave in.

  3. Thanks for posting this article Jc! When I go and purchase hair conditioners, I will be more aware what the ingredients will do since I have a better understanding of adsorption and penetration. (SW)

  4. This totally off-topic but wasn't sure where else to ask so here goes:

    It seems flatirons using steam are the new "it" thing (e.g. babyliss ipro steam, l'oreal steampod). They are advertised as being more effective, gentler, and even capable of conditioning the hair. The claims sound so enticing its easy to get swept up in them. A reality check from you would be great!

    Do you think using steam to straighten hair is less/more damaging than "ordinary" flatirons?

  5. Great summary of the series!

  6. Hi I think your blog is great btw and really helps me to understand my hair and products I use. My question is also about deep coconditioning. My deep conditioner contains hydrolized protein and another coconut oil. You have mentioned that both of these ingredients have benefits when left over night. Wouldn't it be beneficial to leave a conditioner with these ingredients on for longer than 30 minutes so that they can be absorbed? JL

    1. Coconut oil, yes needs an overnight time period because it has to rotate itself to actually penetrate, but this is pure coconut oil not coconut oil in a hair conditioner. Hydrolysed protein appears to redistribute itself overnight spreading further inside the hair. The studies show that the ingredients in hair conditioner can ADSORB (meaning stick to hair) over a period of 20-30 minutes. Beyond this time point, there is no increase, therefore there is no benefit in absorption terms for leaving a hair conditioner longer than 20-30 minutes.

  7. Thank you this is exactly what I was trying to figure out plus so much more about deep conditioning!!

  8. can you PLEASE place a quick and easy donation option on your page..i went to contributions but it didnt have the option there...i dont have a big donation but i would like to drop a dollar in the bucket every time i reap the benefit of your research, skills and effort..THX!

    1. Thank you so much, you are so kind. I love having this blog and commenters like you make me really happy to do this work. I chose not to have a donation button on my blog mainly because I consulted the readers and about 50% were happy and 50% were not. Thank you though for letting me know that you value my work and research :)


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