Human skin exposure to ultraviolet radiation (UVR) from sunlight can cause many adverse effects. Therefore, it becomes necessary to protect the skin from damaging UVR through various means, one of which is through adequate application of sunscreen, especially when exposed to sunlight for prolonged periods of time.
Ultraviolet (UV) light that reaches the surface of the Earth includes both UVB (290–320 nm) and UVA (320–400 nm).
UVB is mainly responsible for redness or sunburn.
SPF is a measure of protection from UVB light.
UVA rays are not directly absorbed by biological targets but they can still dramatically impair cell and tissue functions.
UVA penetrates deeper into the skin than UVB.
This particularly affects connective tissue, inducing the production of detrimental reactive oxygen species (ROS) which in turn damage DNA, cells, vessels, and tissues.
It is important to note that under all weather conditions, the UVA irradiance is at least 17 times higher than the UVB irradiance.
For all these reasons, sunscreens must evidently contain both UVA and UVB filters to protect skin from these two associated harmful rays.
However, patients should be advised that an appropriate sunscreen contains both UVB blockers (e.g. octyl methoxycinnamate, homosalate), as well as UVA blockers (e.g. avobenzone, ecamsule, titanium dioxide, oxybenzone, sulisobenzone, and zinc oxide).
Select a formulation that confers broad‐spectrum protection and to adhere to label instructions for frequency of reapplication.
Inorganic Sunscreen:
They are mineral based sunscreens.
Also called physical sunscreen.
They absorb and scatter the UV rays.
They provide better photoprotection without inducing rosacea flares.
These are products based on zinc oxide and titanium dioxide.
Organic Sunscreen:
Organic sunscreens, such as octyl methoxycinnamate, oxybenzone, and avobenzone, undergo resonance delocalisation when absorbing a photon of UV energy, which results in a change in chemical structure dissipating the UV energy as heat.
They absorb the UV rays without scattering.
This heat warms the face and may flare rosacea.
This chemical reaction does not occur with inorganic zinc oxide and titanium dioxide eliminating the face warming and possibly preventing worsening rosacea. Furthermore, green‐tinted sunscreens have the additional benefit of camouflaging erythema.
