Photo Protection for Hair - Protect Your Hair From UV Sunlight

• Ultraviolet (UV) rays from the sun can damage the color, protein content, and strength of hair
• Darker hair may have more natural photoprotective properties compared to lighter hair
• Topical sunscreens for hair offer minimal protection

Hair Structure

Hair is a complex nonliving structure consisting of three layers:

• Cuticle: Outermost layer. Composed of tiny dead overlapping cells, like roof shingles or fish scales. This transparent layer serves as a protectant for the other layers.^[1]
• Cortex: Middle layer. The cortex is the main component of hair containing keratin and fatty acids that gives hair its strength, flexibility, elasticity, and color (due to natural melanin, or artificial pigment from hair dye).^[1]
• Medulla: Inner core. The medulla contains more loosely packed keratins, fatty acids, and pigment.^[2] This core is only seen in thicker, coarse hairs.

The protein structures of the hair are held together by disulfide bonds, one of the strongest naturally occurring bonds in nature. When exposed to ultraviolet (UV) light, these bonds can become damaged and negatively impact hairs’ natural color and overall integrity.^[3]

Ultraviolet Effects on Hair

The understanding of how hair interacts with sunlight comes from observations of the textile industry. When natural fibers, such as cotton, wool, and silk are exposed to sunlight they become discolored: a process referred to as photoyellowing.^[3] Hair can also undergo the same process when exposed to sunlight.

Human hair is composed of three melanin compounds which contribute to the hair’s natural pigment:

• Eumelanin: contributes brown hues to hair.^[3]
• Pheomelanin: responsible for natural red coloration of hair.^[3]
• Oxymelanin: found in hair exposed to sunlight.^[3]

Oxymelanin is the result of pigmentation breakdown when exposed to sunlight. The level of oxymelanin in hair is directly related to the degree of photoaging or damage to the hair shaft.^[3]

As oxymelanin increases, hair may become lighter with more notable damage. This explains why hair may get lighter during the summertime or after excess exposure to sunlight.

Sunlight not only affects the color of hair, but can also damage lipids within the hair. Progressive damage to lipids responsible in maintaining the strength and integrity of hair can cause hair to become frizzy and more susceptible to fractures (split ends) with combing friction.^[3]

Reactive oxygen species (ROS)

Reactive oxygen species are primarily formed by UVA as a photodegradation product. When both natural and artificial melanin are broken down and oxidized to oxymelanin, they can create reactive oxygen species (ROS).^[1] Similarly, amino acids present within the cortex of the hair shaft also produce ROS upon ultraviolet radiation exposure.^[1] 

ROS are created through a reaction with molecular oxygen (O₂) and a melanin radical. Possible reactions include:^[1]

Melanin + hυ → Melanin*

Melanin* + O₂ → Melanin oxidized + O₂⁻

Melanin + O₂⁻ → Melanin oxidized + H₂O₂

Studies have shown that melanin serves as a protective factor against photodamage.^[1,3] Upon UV exposure, melanin is capable of immobilizing and preventing the formed free radicals (O₂⁻ and H₂O₂) from being transported into the cortex where they could cause progressive damage to the proteins of the hair shaft.^[3] However, during this process, melanin becomes degraded thus leading to the observed lightening effect of hair after UV exposure.

UVA versus UVB

Currently, there is no consensus in the literature regarding specific effects of hair damage from varying ranges of radiation (ultraviolet, visible, and infrared).^[1] However, it is known that UVA is capable of reaching deep into the medulla of the hair shaft and may be one of the main contributors to solar induced hair damage.^[1] UVB may also affect all three layers, but does not travel as deep as UVA.^[1]

How You Can Protect Your Hair From The Sun

Endogenous protection

Interestingly, pigments within hair are the only sources of endogenous (internal origin) photoprotection of the hair and scalp.^[3] The scalp and hair are also susceptible to getting sunburnt! Melanin has been shown to absorb, filter, and displace energy from the sun as heat, which serves to promote photochemical protection of hair.^[1] Even though ultraviolet rays can cause a color change in hair, natural pigments can actually prevent disulfide bond breakage and help preserve the integrity of hair.^[3]

However, the lighter the hair (less natural melanin), the more susceptible it is to UV induced damage. A study comparing the effects of UVA and UVB irradiation to hair found that amino acids in lighter hair colors are more readily degraded compared to that of darker hair.^[4] Thus, blonde hair or advanced gray hair may be more easily damaged by UV radiation than pigmented hair. In other words, darker hair contains more natural melanin and may have more inherent photoprotective properties.

Hair dye

As previously mentioned, pigment is a protective factor against UV induced hair damage. Preserving the cosmetic value of hair by depositing artificial pigment to the hair shaft may be an alternative to protect hair from sun damage.

There are two types of artificial hair dye that can increase the pigment content of hair:

• Semi-permanent: deposits pigment onto the cuticle (outer most layer) of the hair without the use of hydrogen peroxide and ammonia. This simply coats the outer layer of the hair to provide pigment to the hair.
• Permanent: penetrates more deeply into the cortex by “lifting” the cuticle layer with the use of hydrogen peroxide and ammonia, which can be more damaging.^[3]

Dark pigment is typically the result of a mixture of both red and blue hues. Red pigments have been shown to produce superior photoprotection compared to blue pigments.^[3] Red dyes likely absorb more energy from the UV spectrum than blue pigments.

Although hair dying, specifically permanent dye, can be damaging to the hair shaft, the photoprotective effects of providing the hair with more pigment may offset some of this damage.^[4]

Antioxidants

The formation of reactive oxygen species upon UV exposure predisposes hair to damage and lightening. While melanin can help facilitate the neutralization of these radials, those with lighter hair and less natural melanin are at higher risk for hair damage.^[1] Antioxidants may be beneficial to help prevent progressive hair damage caused by free radicals.

Polyphenols are of particular interest as hair protectants. They are naturally occurring compounds, have an abundance of antioxidant properties and are easily attainable through various plants, fruits, and vegetables.^[1] In fact, when an antioxidant formulation of procyanidins from grape seeds, tocopherol, and rosemary was applied to blonde hair as a pre-sun treatment, studies showed that it was an effective treatment in protecting hair fibers from UV-induced ROS damage.^[1]

Examples of polyphenols and their potential effects on hair include:

• Artichokeextract (Cynara scolymus L.): rich in hydroxycinnamic derivatives, protected hair exposed to UV radiation from the lipid peroxidation and protein degradation.^[1]
• Rice extract (Oryza sativa): preserved the strength, color, and luster of hair after UV exposure.^[1]
• Pomegranate extract (Punica granatum): protected the color of dyed red tresses exposed to UV radiation after application of a leave in conditioner.^[1]
• Honeysuckle extract (Lonicera japonica): contains high amounts of flavonoids with antioxidant properties that possess hair protecting properties when exposed to UV light.^[1]

Sunscreen containing hair products

In addition to hair dye and antioxidants, other topical formulations have been designed to provide sun protection to hair. These include shampoos, conditioners, and hairstyling products. However, there is no regulated method of evaluating the efficacy of the photoprotective effects of SPF (Sun Protection Factor) for hair. For this reason, most products are marketed to extend the life of hair dye. These may help prevent blonde hair from becoming “brassy” or brunette hair from developing a reddish hue.^[3]

Shampoo

Shampoos may not provide the most effective method for sun protection. Since shampoos must be rinsed out before styling, it is unlikely that the ingredients contained within the product will be able to remain coated on the hair after it has been washed out.^[3]

Conditioner

A more likely alternative for hair sun protection could be conditioners. Some products contains silicones, such as dimethicone, which leaves behind a thin film that can coat the hair to provide UV protection.^[4] There are two types of conditioners we can consider: instant conditioners, which are instantly rinsed out, and deep conditioners designed to remain on the hair for a longer period of time before being rinsed. The longer the conditioner remains on the hair shaft, the more time the product has to coat the hair. Therefore, when choosing a UV protecting conditioner, a deep conditioner or leaving the conditioner on longer may be a more suitable alternative.^[4]

Styling products

Various styling products may also help provide UV protection. These products include styling sprays and gels. The limiting factor is the degree to which these products can evenly coat the hair. These products are often only applied to the ends of hair, or diffusely throughout without getting an even layer on each hair shaft.

While various hair products may have the potential to protect against solar damage, they may not be the most effective if not applied evenly. It may be more advantageous to use several UV protecting styling products to enhance the protective effects. 

Barrier Protection

In addition to topical products to protect the hair, physically protecting the hair is also a great addition to boost the protective effects! A large brimmed hat with a tightly woven material is a beneficial option to not only protect the hair but also the scalp. More recently, there are new clothing lines proven to protect the skin and hair from UV. Similar to Sun Protective Factor (SPF) in sunscreen, clothing can have Ultraviolet Protection Factor (UPF) which measures how much UV can penetrate through the clothing. The higher the UPF the better!

Summary

Ultimately, the sun can cause pigment dilution, lightening of hair color, and overall physical weakening of the hair shaft.^[3] This damage can impact the cosmetic value of hair causing hair to appear more dull and damaged:

• Texture: increased dryness and porosity, and loss of flexibility.
• Structure: damage to keratins, lipids, proteins, and rupture of disulfide bonds can cause split ends and overall loss of structural integrity.
• Color: damage to melanin can cause unwanted lightening of hair.

While there are products marketed to protect the hair from UV damage, the challenge is finding a product that adequately coats the hair evenly to provide a sufficient barrier of protection. Besides barrier protection, dying the hair a darker color is the only other effective method of protecting the hair from progressive damage.

Practical Tips

• Barrier protection from the sun, such as a hat, would be the most effective method of protecting your hair while in the sun.
• Darker hair colors are more resistant to photodegradation than lighter hair colors.
• Adding dark artificial pigment to hair may help protect hair from UV damage.