Can You Get Wrinkles Through Windows? and Other Beyond-the-Basics SPF Questions

'Tis the season for sunscreen tips, and most beauty junkies have heard them all before: Apply a shot glassful of sunscreen to cover your whole body; choose an SPF of at least 15, preferably 30; reapply every two hours. 

But what about the less talked about details? Already well-versed in SPF 101, we still had a few unanswered questions about preventing sun damage. For answers, we turned to Dr. Jennifer MacGregor, board certified dermatologist at New York's Union Square Laser Dermatology.

What’s the deal with powder sunscreens? Do they really protect skin from the sun? Does any old mineral powder containing titanium dioxide count as SPF? 

While powder sunscreens may provide some level of protection, they have not been studied the same way as cream sunscreens to see if the SPF claims are accurate. The actual level of protection is not known; therefore, you should not rely on a powder sunscreen alone to provide protection from ultraviolet (UV) radiation.

I’ve heard that you can get UV damage through windows, from fluorescent lights and through your clothes. True?  

UVA rays pass through clouds and window glass to cause skin aging, wrinkles and sun spots. The UVB rays are the primary cause of sunburn, but these are blocked by window glass. You can get sun spots and wrinkles on a cloudy day without ever developing a tan or burn. Fluorescent lightbulbs emit a small amount of UV light, but this is far less than that produced by natural daylight. Those typically used in the home or office do not produce a hazardous amount of UV light. Clothing provides some protection from UV radiation, but this will vary according to the fabric type, color and weave. Sun protective clothing will be clearly labeled as such. When in doubt, consult your dermatologist or the Skin Cancer Foundation website for information on a product you are considering.   

If I apply sunscreen in the morning, do I need to reapply before I go outside on my lunch break? Does anyone really do this?  

Broad spectrum physical blockers (containing zinc and titanium) have the best staying power, but no sunscreen should be considered effective for longer than two hours without reapplication. Most people are not diligent about reapplying sunscreen.

Can I wear my SPF moisturizer to the beach, or should I be using a real-deal sunscreen product? 

It is most important to choose a broad spectrum product with SPF 30 or higher and generously reapply every two hours, more often if you are outdoors, swimming or sweating. Those labeled as sweat or water resistant are preferable. New labels for sunscreens should be introduced by the FDA later this year and bottles will be labeled with the recommended time intervals to reapply.  Of course, one should never rely on sunscreen alone to provide protection from the sun. Always wear a hat, sunglasses and protective clothing. Seek shade between the hours of 10 AM and 4 PM and be especially careful near water, snow and sand since they reflect UV light and increase your chance of exposure.

 What areas do people typically overlook when they apply sunscreen? 

People always forget the top of their head, ears and the back of their hands. These are common sites for severe sun damage!

 How long does sun damage take to show up? Are the fine lines I see now a result of tanning I did 5 years ago? 10 years ago?  

It is a myth that our sun damage was ‘done’ in childhood and suddenly shows up later. In fact, we get less than 25% of our sun exposure before the age of 18. UV rays start to damage skin within minutes of sun exposure and there is a slow, constant accumulation of the physical signs of aging throughout life. Prevention is an essential part of a healthy lifestyle for both children and adults of any age.