Damaging Effects of UV Radiation on Hair

Damaging Effects of UV Radiation on Hair

I was recently in the beautiful land of sea and sun aka Barbados (my homeland) for a few days and man was it hot.  The sun was so scorching hot that I started to wonder about the effects it was having on my hair.  We all know that we should protect our skin from those harmful UV rays but I was curious about if those same rays were impacting my hair in any way.  The short answer is yes, so the next questions for me became: “How does UV radiation damage the hair?” and “Is there any feasible way to reduce the amount of UV damage to my hair without wrapping my head like a bandage each time I venture outdoors?”   In this post I sought to find answers to those 2 questions.  I will share my findings.

According to a study by Croda Inc., hair is susceptible to UV damage and relaxed hair particularly susceptible because it has been subjected to chemicals with high pH.  Our hair is acidic and to permanently straighten (or relax) the hair, high alkaline chemicals are used to alter the natural curl pattern.

Croda’s study sought to determine whether hair treated with a polyester polyquarternized UV absorber – Polyquaternium-59 and butylene glycol (PQ-59) could “mitigate UVB-induced damage in hair”…preserving the hair’s “natural hydrophobicity, fiber strength and combing properties” in relaxed African-American hair.

To measure the effects of UV radiation on hair, the study used three parameters namely hair surface damage, hair surface hydrophobicity and tensile strength to determine how effective PQ-59 was when compared to traditional sunscreens (ethylhexyl methoxycinnamate or OMC) and standard shampoo base in preventing UV damage.

Hair surface damage – to measure this parameter they analyzed an amino acid called trytophan.  Tryptophan is found in the hair and decomposes when exposed to UV radiation.   Therefore if the hair is exposed to UV radiation and the level of tryptophan decreases, it is a strong indication of UV damage.

Hair surface hydrophobicity – “Healthy virgin hair is normally hydrophobic [not readily absorbing water] however, when hair is exposed to UVB radiation, hydrophilic [readily absorbing moisture] groups tend to form on the surface, making it less hydrophobic. ” In other words, if hair is exposed to UV radiation and the hydrophobicity of the hair decreases, it is an indication of UV damage.

Tensile strength – “UVB radiation penetrates the cuticle and damages the cortex of the hair.  This damage is measured by the hair’s tensile strength or susceptibility to breakage.”  Therefore, a decrease in the amount of stress required to break a hair strand after exposure to UV radiation is an indication of UV damage.

The results from the study revealed the following with regards to the three parameters:

  1. Hair treated with PQ-59 preserved the most tryptophan at 71.5% as compared to hair that was treated with traditional sunscreen (OMC) and standard shampoo base (14.4% and 0% respectively)
  2. Hair treated with PQ-59 experienced minimal degradation of the hydrophobic properties of the hair and
  3. Hair treated with PQ-59 experienced a 4.2% reduction in tensile strength as compared to a 12.5% reduction with OMC and 16.1% reduction from standard shampoo base.

UV exposure irreversibly damages both the hair exterior of the hair shaft as well as the cortex (interior).  The study showed that PQ-59 did a superior job at protecting relaxed hair because when applied before exposure to UVB rays, relaxed hair did not experience as much “protein degradation and loss of integrity” as when traditional sunscreens were used.

Which products have in this PQ-59 compound?
Not many that I could find to be honest.  Most of the products I found are brands that are either not easily available to me or I’m uninterested in trying such like Bumble and Bumble, Creme of Nature Nourishing Permanent Hair Colors and John Freida Frizz-Ease.  Long story short…I’m no closer to protecting my hair from those harmful UV rays than when the thought first popped in my mind. If you are aware of any other products with this special UV absorber be sure to drop me a line and let me know.

Obukowho, Patrick; Gao, Tim; Woldin, Barbara – Croda Inc. Photoprotection of relaxed hair: Croda details new data on its UVB absorbing polyester polyquat. (2004)?

Author: Vogue

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1 Comment

  1. I came across your article researching a product that I am using (and loving) that contains Polyquaternium-59. In response to your question about which products contain it, Ouidad Moisture Lock Leave-in does. My hair is relaxer free but I do have hair color. My experience with the product has been nothing but a blessing considering the summer months/heat and the drying effects of the hair dye on my fine hair strands.

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