In part 2, we talked about the effects of UV radiation on the hair, and today we will talk about how photo-oxidation denatures the protein in your hair.
Photo-oxidation targets the cystine amino acid in keratin protein which is converted to cysteic acid. This is what is referred to as denaturing of protein. This will result in the fusing together of the cuticle surface, which will gradually open/crack and eventually lead to cuticle loss due to loss of strength and flexibility.
Photo-oxidation of the lipids really is the oxidation of polyunsaturated fatty acids. For this discussion we will limit the definition of lipids to essential fatty acids. The mechanism is oxidation of the double bonds for mono and poly unsaturated fatty acids (lipids). With the loss of the cement that holds the cuticle in alignment, the cuticles open and allow further damage to occur at the cortex.
While it is true that dark hair is less susceptible to UV damage than blonde hair (due to melanin content), damage still can occur as a result of overexposure to sunlight. Visible radiation is responsible for bleaching, i.e., the oxidation, of melanin of the hair. It’s the combination of damage to the protein, lipid and melanin that results in dryness and increased porosity. The hair rapidly losses tensile strength and breakage occurs.
Let’s conclude this discussion with “so what”. What does this mean to you?? Why is this important to the health of your hair? Remember, UV stress leads to misalignment of cuticles, which leads to hair dryness, and ultimately hair breakage. We are not proposing that UV stress is the only cause of hair damage. We are merely educating people on the 6 possible causes of hair damage and breakage. In actuality, it is normally a combination of several types of stresses, which results in breakage. Our hopes are that you will be thinking about your daily activities as it relates to UV exposure. This will be an open forum and please feel free to ask questions.
- Here’s some discussion questions you may want to think about.
- How much time do you spend in sunlight during your daily activities?
- Do you know the effect of seasons on your hair as it relates to UV radiation?
- Do you know at what time of the day is UV radiation is the strongest?
- Do you live near water, snow or sand?
- Do you understand how reflection can increase UV radiation?
- What sunscreen protection are you currently using?
- Tip: A simple hat is the best protection!Do you live in a high altitude location?
- Do you know the relationship between UV exposure and altitude?
- Do you use tanning salons or sun lamps?
- Do you protect your hair during tanning sessions?
- What type of lighting do you use at home, school or in the office?
- Did you know that Mercury Vapor Lighting is a source of UV radiation?
- Where do you live in relation to the equator?
This discussion will be food for thought for how to think about UV stress. After all the types of hair stress have been discussed (Yes, we have five more to cover), we will cover how to prevent or minimize the damaging effects of stress. When we discuss the solutions it will be in the context of products and ingredients. We will look at each product type and discuss the pros and cons as it relates to the 6 hair stresses. We will also look at current products on the market and why you should consider a natural alternative (CUSH). Again, this approach is from the perspective of ensuring healthy hair. If you know how hair is damaged, then you can use products that will minimize the possibility of damage/breakage.
Our next discussion (part 4) will be on thermal stress! Leave the flat irons and blow dryers home for this discussion :)
We recently spoke about how the misalignment of the cuticle is one of the dominant causes of dry hair. Stress to the hair follicle is what causes misalignment of hair cuticles. I have grouped together the classic 6 types of stress for our discussion. Today I will focus on ultraviolet stress (sunlight) and why and how it can damage hair. However, before we can discuss ultraviolet stress to the hair, we need to briefly talk about the chemistry of hair.
Chemistry of Hair
There are 3 predominant types of bonding in the hair structure: Hydrogen Bonding-gives the hair elasticity; Salt Bonding-gives the hair structure and some elasticity, and lastly Disulfide Bonding –which gives the hair the most structure. We will focus on the disulfide bond because it is primarily responsible for hair structure and the most susceptible to damage by photo-oxidation. So what exactly is a disulfide bond and why is it the most important bond for your hair?
The hair fiber is made up of 85% alpha keratin protein. Alpha keratin protein provides structure to hair. Thus it is commonly referred to as a structural protein. Keratin protein and any other protein for that matter are comprised of long chains of amino acids linked together with peptide bonds. (By now, you’re probably thinking what does this have to do with disulfide bonds? Everything! So be patient and please keep reading). There are 20 very unique amino acids associated with protein in living matter and they are the building blocks of life (i.e. your hair and skin, etc.) The predominate amino acid in keratin protein is cysteine. Cysteine amino acid is unique because it contains a sulfur side group (thiol). When a keratin protein chain aligns itself with another thiol group, it forms a disulfide bond. This disulfide bond configuration of two cysteine amino acids is referred to as cystine. It is the cystine structure that gives hair its structure. Now, back to UVA/UVB as a hair stressor.
Sunlight is comprised of visible radiation, ultraviolet radiation type A (UVA) and ultraviolet radiation type B (UVB). Radiation is energy and we can thank the depletion of the ozone layer for its increased intensity at the earth’s surface currently. UV radiation penetrates the hair’s cuticle and cortex. The intensity of the radiation is more concentrated on the cuticle surface than on the cortex; thus damage to the cuticle is disproportionally higher. With that said, a damaged cuticle surface exposes the cortex to further damage in the future.
Radiation associated with sunlight attacks keratin protein, lipids (cellular membrane complex) and melanin. As I stated earlier, keratin protein is responsible for the hair structure and the lipids act as glue to hold the cuticle layers in place. Melanin gives hair its natural color. When hair is over exposed to visual and ultraviolet radiation, it results in hair that is bleached, brittle and stiff. Therefore, it is more susceptible to breakage.
Find out more about UV Rays in part 3.
There’s been a lot of discussions on hair dryness and which products are most effective at restoring moisture back to the hair. The most important thing to know is what is the “definition” of dry hair and how did it become dry. Once you’ve confirmed that your hair is dry, and you know why it’s dry, you can put a solution into place to over come it. So let’s begin with the definition of dry hair, and segue into the many culprits that lead to this stressful condition.
What is Dry Hair?
Dry hair is defined as hair that lacks the ability to maintain adequate levels of hydration. Untreated hair’s moisture content is approximately 10% at atmospheric conditions. When hair is not properly hydrated, it becomes less elastic and has a physical feeling of dead grass or straw. So, what’s really happening with the hair scientifically?
Your hair is comprised of three layers: the medulla (inner layer), the cortex (the middle layer, and the cuticle (the outer layer). A very basic description of the hair shaft includes both the cuticle and cortex. The cuticle is the layer of sheathing that protects the cortex. Protecting the cortex is the most critical thing that you can do to ensure healthy hair because the cortex gives hair its elasticity and strength. The cortex houses most of the keratin protein; and therefore, contributes the most to the mechanical property of your hair, i.e. will it stand strong or become limp. Needless to say, when the cuticle becomes damaged, well you get the picture, your hair can become damaged and dry because the cortex is now exposed to harmful stressors. What causes cuticle and ultimately cortex damage?
Generally, mis-alignment of the cuticle is one of the most common causes of dry hair. Other stressors could include the following:
Alcohol Based Gels
Now that you know what dry hair is and what causes, check back tomorrow to discuss the first of the stressors-UV Stress.