While the industry and general public are highly educated about the dangers associated with excessive exposure to sunlight, especially the UVA and UVB wavelengths, findings in recent years reveal that the full spectrum of benefits and harm related to sun exposure are yet to be explored. One of the more striking recent discoveries is that while UVA and UVB are indeed responsible for skin damage, high energy visible (HEV) light, i.e. in the violet and blue range, may cause as much damage as UVA and UVB combined.1–4 However, developing a compound to shield the skin by the selective filtration of violet and blue light presents challenges in molecular design as well as formulation because an effective compound must exhibit color.
UV absorbers in skin care formulas do not impart color because the retina does not respond to the range of photon energies they absorb. However, since HEV absorbers selectively reduce, for example, violet and blue light from the visible spectrum, the eye perceives this as a change in color as the remaining spectrum is expressed; in this case, it appears brown or yellow-brown.
In this paper, the authors present the rationale behind the development of a fractionated melanin (FM) that is tailored to absorb light in the HEV blue to violet wavelength range of 400–500 nm, with minimal absorption in the red range. Since it provides UV as well as HEV photoprotection, it imparts color to formulations. Therefore, the present paper also suggests approaches to cope with the aesthetic challenges this molecule presents when introduced into semi-solid formulations. Overall, this material is presented as a novel means to maximize photoprotection and phototherapy while minimizing its color footprint.
HEV Light and Skin
HEV light is in the blue to violet band, 400–500 nm, of the visible spectrum. The effects of HEV light on macular degeneration have been studied and results suggest it may be a key factor in this age-related disorder.5 The mechanism by which the light damages the lens and retina of the eye is believed to be the generation and accumulation of reactive oxygen species (ROS) that lead to oxidative damage to cells and their organelles. These changes are irreversible and should therefore be minimized as much as possible. In relation to skin, two independent studies were conducted to evaluate the effects of HEV light, which demonstrated photodegradative effects similar to those found in the eye to the epidermal and dermal tissues.