UVA and UVB are the harmful sunrays that reach our earth’s surface. UVB rays are largely absorbed by the outer skin layers and are responsible for causing sunburn. Greater amounts of UVA rays however penetrate deeper into the skins living layers and are also highly damaging. UVA induced skin damage can occur without the skin burning. UVA is responsible for causing accelerated ageing of the skin (photoageing).
Recent research has highlighted an increasingly important role for UVA in the causation of skin cancer, not just UVB.* UVA also reduces the skin’s ability to identify and destroy early skin cancers. In families prone to skin cancer, UVA has been shown to have a greater suppressive affect on their skin's immune system, resulting in the development of more and more skin cancers over time. This is a particularly important issue for patients on immunosuppressive therapies following organ transplant.
Many Sunscreens on the Australian Market do not adequately protect against UVA rays. Sunscreens contain UV absorbing ingredients, which protect you against the sun's harmful rays. Unfortunately, the UV-absorbing ingredients of many sunscreens on the market are not photostable, particularly at UVA wavelengths. This instability causes some sun protective ingredients to degrade with sun exposure, thus reducing UV protection. This degradation can begin to happen within just one hour of application. To be sure you are protecting your skin in an adequate way; you need to use a photostable broad-spectrum sunscreen.
Increased UVA toxicity in a range of common skin and medical disorders means those individuals particularly require sunscreens with a high level of UVA protection. If you are using over the counter and prescription treatment products for acne or rosacea including retinoids, benzoyl peroxide, and salicylic acid, along with those on tetracycline antibiotics, metronidazole or isotretinoin for example have greatly increased sensitivity to UVA. This similarly occurs with many other antibiotics including the quinolones, sulphonamide anti-microbials, along with diuretics, anti-arrhythmics particularly amiodarone, and chemotherapeutic agents including the new targeted TKI’s such as erlotanib. Anyone using any of these agents from Spring to Autumn must also use a sunscreen providing a high level of UVA protection. Ask your doctor for a recommendation if you are unsure.
The importance of UVB for vitamin D production by the skin also emphasizes the benefits of more balanced sun protective products that do not provide far greater UVB than UVA protection. Studies increasingly link low vitamin D levels with a number of internal risks including cancer.
Ultraviolet A within sunlight induces mutations in the epidermal basal layer of engineered human skin,Huang XX, Bernerd F, Halliday GM. Am J Pathol 2009 Apr;174(4):1534-43.