How to achieve a broad spectrum tanning

Traditionally sunscreen products have focused on UVB protection, and during the last decade also on UVA protection. Scientific studies clearly demonstrate damages in human skin originating from exposure to UVA radiation - in particular related to photo ageing and to the severe skin cancer malignant melanoma.

Recent documentation also demonstrates a risk from visible blue light radiation. Even though the mechanisms of these damages are poorly understood, there is little doubt that both UVA light and visible blue light is harmful, responsible for substantial degradation of the skin’s structure as well as instability and mutations in the skin’s DNA.

Basal cells form the base layer of the epidermis.
Basal cell carcinoma develops in the basal cells, and is the most common skin cancer in humans. Although it is a slow growing cancer it can be very destructive and disfiguring. Basal cell cancers rarely metastasize, and the cancer can usually be cured when detected.

Keratinocytes (also called squamous cells) are the major cell type of the epidermis, constituting 90% of the epidermal cells. They have their origin from stem cells in the basal layer, and end their life as dead cells in the stratum corneum.
Squamous cell carcinoma is a skin cancer that originates in the keratinocytes. The cancer can be lethal because of its ability to metastasize (move to other, healthy parts of the body).

One way of describing light is in terms of waves. The length of the waves – wavelengths - can be translated to energy, as shorter wavelengths are higher in energy. The penetration of light through any material depends on the wavelength: Shorter wavelengths are more likely to be reflected while longer wavelengths penetrate. This is why longer wavelengths penetrate the skin more deeply than shorter wavelengths.

The stratum corneum is the upper part of the epidermal skin layer. It consists of dead, flattened cells with a high content of the fibrous structural protein keratine. The stratum corneum is important to the skin’s strength to outer stress, and skin located at e.g. the soles of the feet has a thicker stratum corneum with a higher content of keratin.

The dermis is below the epidermis and contains a number of structures including blood vessels, nerves, hair follicles, smooth muscle, glands and lymphatic tissue. The layer also has a high content of collagen and other elastic materials important to the skin’s strength, its ability to fight off infections and repair itself. Effects like ageing and wrinkling of the skin is much due to a breakdown of the elasticity of this layer.
The dermis is below the epidermis and contains a number of structures including blood vessels, nerves, hair follicles, smooth muscle, glands and lymphatic tissue. The layer also has a high content of collagen and other elastic materials important to the skin’s strength, its ability to fight off infections and repair itself. Effects like ageing and wrinkling of the skin is much due to a breakdown of the elasticity of this layer.

Solar radiation penetrating the atmosphere consists of Ultra Violet (UV), visible light and Infrared (IR) wavelengths. The radiation penetrates the human skin with different efficiency, higher wavelengths penetrating deeper into the skin than lower. Overexposure of sun rays can cause burns and DNA deformations leading to skin cancers, damages to the immune system and other photo damages like photo ageing.
When sun rays hits the skin surface it consists primarily of infrared and visible radiation, with only a small portion being within the Ultraviolet spectrum. The portion of UVA rays are about 10 times higher than UVB rays. This means that even though the UVB rays induce skin damage more efficiently, UVA and visible rays reach the cells of the skin more frequently.
Most of the solar radiation induced skin damage is done in the top skin layer, called epidermis. The epidermis is protected by the stratum corneum, a layer of dead cells. Important cells in the epidermis are Basal cells, Melanocytes and Keratinocytes.

UVB, UVA and visible blue light radiation are all important in the induction of skin cancer in humans. Skin cancer can originate in either of the three cell types of the epidermis, causing Malignant melanoma (malignant tumour of melanocytes), Squamous cell carcinoma (malignant tumour of keratinocytes), or basal cell carcinoma (malignant tumour of basal cells). Malignant melanoma is the most severe skin cancer with a mortality rate of approximately 50%.

UVB rays are the main cause of erythema (sun burn). Previously it was believed that UVB rays where the only rays capable of inducing DNA damage and skin cancers. Today’s knowledge reveals that rays in the UVA spectrum (and in the visible blue light spectrum) play a significant role in the cancer induction.

Few studies have been done on the harmful effects of visible blue light radiation. However, recent research shows that DNA damages are indeed induced by solar radiation in the upper UVA and in the visible blue light region - a clear indication that also the lower energy wavelengths can have a significant impact on the skin’s health.

Applied to the skin surface, sunscreens act by absorbing or reflecting rays in the UVB and partly UVA parts of the solar spectrum - preventing solar radiation induced damages on skin cells. Today’s sunscreens, however, do not give sufficient protection against upper UVA and visible blue light rays. As today’s filters allow us to spend more time in the sun without getting burned, researchers worry that we are over-exposed to UVA and blue light.

Absorbing sun rays in the UVA and blue light range of the solar spectrum, combined with a UVB sunscreen, will add the ultimate broad spectrum protection to a sunscreen composition, preventing the damage of important cellular molecules.