A Scientific Response to Ouidad’s Claim: ‘Oil Does Not Seal in Moisture’

As much as I am a blogger and writer, I am also an avid reader of BGLH and I did not miss the recent video highlight of Ouidad discussing hair and her opinion on using oil on hair. To be specific the quoted portion from the conversation,

‘Oil does not seal in moisture. Oil coats the hair and repeals natural moisture [from the environment]. It causes dehydration, dullness, and frizziness. Our hair is like us, it needs to breathe. If we suffocate it [with oils], it dries out.’

Just Grow Already Oil Sealing Experiment 

Q1: Semantics – does oil really seal in moisture?

When a natural says ‘I use oil to seal in moisture’, they usually mean that after applying water or a water based product to hair, a film of oil is used to help prevent moisture loss. This is the question I will address and not the semantics of whether the right word is seal or coat.

Q2: What does science say on oil and moisture?

A scientific study looked at the effect of applying oil to hair on both moisture retention and moisture pick up from the air (Journal of Cosmetic Science, pp 135-145, 2007). The oils used were coconut, sunflower and mineral oil. The 3 key findings were:

Oil DOES help to prevent moisture loss from the hair fibre. Hair with an oil layer has higher moisture retention compared to uncoated hair.
Oil DOES have a sealing effect. Hair with an oil layer will take up less water vapour compared to uncoated hair which means that the oil layer slows moisture uptake. Coconut oil allowed more moisture in than mineral oil (i.e mineral oil is a better sealer).
Oil layers on hair DO NOT prevent hair from taking up water vapour. Although uncoated hair will take up the most water vapour from the air, hair coated with oil (mineral, sunflower or coconut) will also still take up significant amounts of water vapour from the air.

The final conclusion of the study was that oil films on hair slow the loss of moisture from the hair creating a moisturising effect.

Q3: What exactly is in the glaze product suggested for shine instead of oil?

The Ouidad shine glaze serum suggested as a final touch for shine contains two silicones (silicones are oils), alcohol and an emollient (Cyclopentasiloxane, Dimethiconol, Alcohol Denat, C12-15 Alkyl Benzoate). It is pretty much a silicone based serum that will feel less oily due to the emollient. In the grand scheme of water entry prevention to hair, silicones and mineral oil are top of the table.

Q4: Does oil suffocate hair?

Since a significant amount of water can still get into oil coated hair (even mineral oil coated hair), no, oil cannot suffocate hair. It simply takes a little longer to get water in but equally, water that is underneath the oil layer, takes longer to get out.

Q5: Does oil prevent water from entering hair?

No, there is no oil that can form an absolute barrier from water entry to hair. If you chose to dunk your head in a tub of oil and then went into a shower, your hair would still get wet because despite all that oil, water can get in!

Q6: Will a thicker oil coating slow down moisture uptake from the air?

Yes, the thicker the oil coating on your hair, the lower the uptake of water from the air. A light film will allow more water uptake from the air. You can experiment with light or heavy oiling to find out which one suits you best, there is no universal correct method.

Q7: What if you do experience dry and dull hair when using oil?

First, always feel free to add water to your hair should it feel dry, the water will penetrate past any oil layer. You can also use less oil and opt for a light natural oil (jojoba, sunflower, coconut, almond) instead of silicone or mineral oil. However, if oil is not for you, this is also fine, respect your hair!

Ladies, what are your thoughts?