Importance of Sunscreen/Sunblock
I reviewed a Special Report insert in the April 2011 The Dermatologist journal that was very informative about the need and use of sun protection. It details the difference in effects of UVA vs UVB rays. I will summarize the main points. It is critical to educate patients about the following information.
UVA and UVB are the rays that are important in skin disease and aging. UVA comprises 96.5% of UV radiation and UVB comprises only 3.5%. (Remember that SPF only tells you how much of the UVB is blocked, although UVB is important in damage to the skin). UVA can penetrate glass and reach the skin’s dermis, while UVB cannot. UV radiation causes DNA damage, immunosuppression, and sunburn.
After UV exposure, melanin (pigment) synthesis is a mechanism to combat UV damage. Melanin blocks UV and scatters UV radiation to prevent damage. This is why darker skinned individuals do not sunburn as easily and do not show as much sun-induced aging and skin disease/cancer. UV-induced immunosuppression is associated with increased risk of skin cancer.
Sunburn is due to UVB radiation. Long-term effects of UV radiation are the obvious signs of photoaging, skin thickening, pigment disorders, and skin cancer. Photoaging is caused by both UVA and UVB. However, UVA reaches the deeper dermis of the skin and induces reduction of collagen, fibrillin, and elasticity. This is what leads to lines, wrinkles, laxity, and brown spots.
Skin cancer can result from UV exposure. Acute exposures (sunburn) are associated with melanoma while chronic UV exposure is associated with squamous cell carcinoma. This is why sunblock can prevent cancer.
Pigment disorders, such as solar lentigos (brown spots), melasma and post-inflammatory hyperpigmentation are the result of acute and chronic UV exposure. Even dark skinned patients will notice progressive darkening of the skin and uneven pigmentation. Sunblock will greatly reduce the risk of these conditions in all skin types.
Tanning beds emit mostly UVA radiation (the more cancer causing rays). This is about the worst thing you can do to your skin!
Melanin (pigment in the skin) clearly protects from UV radiation. But as previously mentioned, darker skinned patients can still suffer from the effects of the sun, so sunblock is still important.
Physical blockers like zinc and titanium mainly scatter and block sunlight from entering the skin. Most studies that I have read show that zinc blocks UVA much better than titanium. I tell my patients that sunblock must have zinc in it to block UVA. Over-the-counter zinc sunblocks are usually thick like tooth paste. Medical grade sunblocks (i.e. EltaMD and SkinMedica) have micronized zinc and are absorb into the skin nicely without leaving a white residue. Patients can easily use them under makeup.
It is also important to know that zinc must be absorbed into the skin to work. It has to sit in the skin to reflect the rays. This is why I always tell patients that they have to use a separate sunblock and not count on the “SPF” in their makeup.
In contrast to the physical sunblocks (zinc, titanium), chemical sunscreens absorb UV rays. These typically only absorb UVB rays so they need to be combined with zinc for “full-spectrum” coverage. Contrary to what the bottle might say, it is not really full-spectrum coverage without zinc (UVA protection). Other ingredients may block a small percentage of UVA, so they can legally say it blocks UVA, but it is a minimal coverage of UVA without zinc.
The role of sunblock in vitamin D deficiency is controversial. I believe that it is simply taken care of by making sure that the patient gets enough vitamin D in their diet and that levels are checked with yearly routine blood work (yearly visit to your doctor).
SPF only refers to UVB protection. An SPF of 30 blocks 96.5% UVB and SPF45 blocks 98% UVB. You are not wearing a “stronger” sunblock if the SPF is greater than around 40. It must have zinc in it to properly block UVA. There will soon be a new rating that will tell you how much UVA and UVB is blocked. No sunblock is truly waterproof. The ones my practice provides are water resistant.
No sunblock lasts longer than 80 minutes. Reapplication every 1.5 hours is key! Sunblock must also be applied to dry skin and 30 minutes before sun exposure to be fully efficient.
Topical antioxidants in sunblocks and used in a separate product improve protection and decrease inflammation. They act as free-radical scavengers to prevent inflammation from UVA rays. Among the good antioxidants are Vitamins C& E, green and white tea, grape seed extract, and others. Oral antioxidants can also provide photoprotection.
Sun protective clothing is also popular and efficient. Certain items like wide-brim hats now offer an SPF rating.
- Use a full spectrum sunblock with zinc. The SPF doesn’t really matter above about 40. It must contain zinc.
- Apply 30 minutes before sun exposure and every 1.5 hours.
- UVB is more responsible for sunburn and UVA is more responsible for deeper damage. Both cause photoaging and skin cancer.
- Don’t count on your makeup or moisturizer as a sunblock. It helps, but you need to use a separate sunblock.
- No tanning beds! I tell my patients that getting some sun and color is understandable, but slowly and through good sunblock. I don’t expect them to be a vampire!
- Topical and oral antioxidants can help reduce the effects of the sun.
- Proper use of the right medical-grade sunblock can significantly reduce visible signs of aging and diseases of the skin and skin cancer.