Can Heat Permanently Damage Natural Hair?


So I was browsing some of my fav natural sites today and came upon a pretty controversial topic in the natural hair community - hair straightening using heat.

You may have already been hearing some Naturals say straightening is bad for your hair. You may have also heard the varying angles and perspectives as to why. There is the social/ideological angle arguing that straightening hair, regardless of how you do it, is an act against the full acceptance of our natural hair and, to some, ourselves as a whole.  I personally don't have much of an opinion about this  idealogical view  other than to say; 'to each his own'.
What struck me had to do with the physical and impactful consequences on hair that has been straightened using heat.

My scouring of the online natural world turned up Naturals, left and right, recounting their horror stories of heat-straightening leaving them with permanent changes in hair texture (loosening of curls that have not reverted back to their natural state), more breakage than normal and generally frizzy, dry hair. And much like the toppling of dominos, these stories spread and has, in turn, lead other Naturals and newbies to swear off straightening for fear it will permanently damage their hair as well. 
Effectively the question that seems to puzzle us all is this: Can heat really permanently damage hair? Some say yes and insist they have firsthand experiences to show, while others, who have been straightening for years emphatically dispute this conclusion, remarking the consistent health of their hair even after years of heat application.
My answer to this question is based on my understanding of the chemistry behind the process of heat-straightening and it is: Yes and no! Frustrating answer, I know, but read on, you might learn something.

My goal is to shed some light on how heat works to straightens hair and thereby (hopefully) dispelling the fear that heat will permanently damage our precious curls.
So here goes (Remember I'm from a health/bio/nutrition background so expect to get the low-down - stay awake. lol):

The Chemistry of Hair
Hair is made up of a protein called alpha-keratin. This unique permutation of the keratin protein is what lends hair its resistance and pliability, both wet and dry. Like all proteins, alpha-keratin is identified by the amino acids (bio-molecules) that make it up and the way those molecules are arranged (called the structure of the protein).

You may or may not remember from your bio class that proteins are formed by the multiple foldings of their polypeptide chains (linked molecules). The multiple foldings of proteins are categorized as the following: Primary, secondary, tertiary and quaternary structures. Think of these structural classifications  as dimensions (though it's really not). Each structure reflects an added level of complexity in the folding of the protein molecule. The primary structure refers to the most basic, but core structure, while the tertiary and quaternary structures refers to the protein's final shape with all its complicated folds.
If you are still with me, I'm impressed. :)

We won't bother at all talking about the primary structure of proteins since it is  not generally affected by heat, pH or cosmetic products.  And we'll barely talk about the secondary structure as it is rarely, if at all, affected by heat. What we will talk about (the structure affected when we apply heat to our hair) is the tertiary structure of the hair protein.  This tertiary structure of the alpha-keratin hair protein is formed almost exclusively with folds held in place by hydrogen bonds.

It is important to note, though, that some hydrogen bonds also form the secondary structure of the hair protein.  This explains why heat may affect the innermost layers of a hair strand. Also, of note, is that the more impact there is to the more innermost layers (structure) of the hair strand the more irreversible the alteration/damage (of the keratin, this is called protein denaturation).

Knowing this, the implications of  too high heat for too long is that it can result in irreversible alteration to the structure of hair....but let's back up.

What Are Hydrogen Bonds?

Hydrogen bonds are responsible for the curl that exists in your hair, and, in the tertiary structure of the keratin protein, it looks something like this.
The H in the pic represents the hydrogen bonds that pull the hair fiber into its naturally curled/coiled state.

How Heat Affects Hair Strand
 When you apply heat to hair, assuming the heat level is not too high, the hydrogen bonds of the tertiary structure are affected first.  The keratin hair protein undergoes what is called denaturation, which simply refers to removal of the protein bonds. In this case, the hydrogen bonds making up the tertiary structure are removed, and thus the curl/coil pattern is loosened or removed.
Once hair is no longer exposed to the heat(hair cools), new hydrogen bonds may form on the hair's new  (straightened) shape.  This is what allows hair to maintain its straight texture for some time. However, hydrogen bonds are attracted to (and thus broken by) the slightly negative charge on the oxygen end of water molecules. This means water will break the hydrogen bonds formed after heat-straightening and explains why hair reverts back to its curly/coily state when wet.

Too Much Heat
 When high heat is applied to the hair strand for excessive periods of time and when hair is not allowed to 'normalize' after heat processing, the damage may become irreversible.  The general takeaway is that heat does not permanently damage hair.  But this statement assumes that hair is not subject to excessive heat  (as in enough to fry the hair) and not for more than a few seconds at a time.  Under normal heat conditions, the hydrogen bonds will reform when heat is removed and the hair will revert to its natural shape over time (and with water).
Too much heat damages hair by not only removing hydrogen bonds at the tertiary level but by removing the hydrogen bonds that make up the more inner  (secondary) structures of the hair protein.  The removal of a large number of bonds makes it difficult for the keratin protein to revert back to its natural shape.  And because the function/characteristics of a protein is tied to its shape, the characteristics inherent to the keratin hair protein are lost. For hair, this means loss of elasticity/pliability, loosened curl patterns, and less resistance to breakage.

Heat Control
If you do want to use heat to straighten your hair, apply these measures:
  • Choose the lowest setting that will straighten your hair. If the medium setting gives you results, don't switch to the high setting. The hair will either straighten or it won't. Higher settings just risks breaking more bonds in your hair, and risking irreversible effects.
  • Use a heat protectant product. These products are meant to offset the effects of heat on your hair by offering an added layer of protection. They should lessen the amount of heat that goes into the hair strand.
  • Be gentle with hair. Hair altered in any way is weaker than in its original state. Hair that has been straightened has had an extra layer of protection (the pliability of hydrogen bonds) removed and thus is inherently more brittle and less resistant to breakage. Be gentle during and after straightening.

'Normalize' Hair Between Straightening
 Healthy hair forms optimal levels of hydrogen and salt bonds.  Hydrogen bonds are affected by oxygen  (think water), nitrogen, and other highly electronegative molecules. This means that exposure to anything largely made up of these will reduce optimal hydrogen bonding in your hair.
Salt bonds are affected (including broken) by pH imbalances.  The less of these salt and hydrogen bonds making up your hair strand, the more susceptible your hair is to the damaging effects of heat when you do apply heat.  To return your hair to normal, between straightenings, treat your hair to deep treatments  (protein or moisturizing depending on your hair needs), and maintain proper moisture. Also keep handling of hair to a minimum as bonds, specifically salt bonds, can be broken simply by manipulating hair.

This post was about informing you so you can be confident that you are making good decisions for your hair while still having the freedom to just have fun with it. Hope this help shed some light on this much-debated topic.
For those of you Natural researchers still curious and want to know more, check out these sites:


ChoQolate ChiQ BKA QD! said...

Thank you for sharing!!