Bottle of sunscreen a day does much to keep sun rays at bay

People who spend entire days on the beach or on the water should each be going through a whole bottle of sunscreen, advises a Johns Hopkins expert on dermatology. 

Dr. Mary Sheu, an assistant professor in the department of dermatology at the Johns Hopkins University School of Medicine, said the general rule of thumb when applying sunscreen is to use a shot glass-sized amount and reapply every two hours. 

“You should go through an ounce of sunscreen for your whole body every time you apply. That’s about the size of a shot glass. If you reapply every two hours for each person, you’re going to go through a bottle of sunscreen, depending on the size of the bottle. If you have 4-6 ounce bottle, reapplying it every other hour and more often when you’ve been in and out of the water and you’re on the beach all day, you should go through the bottle,” Dr. Sheu said. 

She also advised anyone who spends time in the sun – which is basically everyone who lives in the Cayman Islands – to opt for a higher factor sunscreen than they think they might need.  

“We should use SPF that is 30 or higher – that is the minimum. The higher the better,” Dr. Sheu said. “That is partly because when we use sunscreen in real life, it’s very different than when the manufacturers test it. They put on a much thicker layer than we do in real life. 

“When it says SPF factor 30 on the label, we might be getting factor 10 or 15. I think going higher definitely protects us more.” 

She added: “In real life, when using factor 15, we’re might really be only getting a protection level of 4 because we use so much less sunscreen.” 



People with rosacea – a chronic skin condition that makes the face turn red and may cause swelling and skin sores that look like acne – should be aware that sun exposure is a trigger for the condition.  

“Many people notice their skin turns more red and it causes more pimples for them. Sunscreen should be used on a daily basis for people with rosacea,” Dr. Sheu explained. 

Using sunscreens with ingredients that offer a physical barrier to the sun’s rays is the best option for people with rosacea or with sensitive skin. Dr. Sheu advised people with the condition to opt for brands containing zinc oxide or titanium dioxide, or a combination of both, which form a barrier against the rays, instead of sunscreens that offer only chemical protection. 

“The chemicals in sunscreens absorb the UV rays from the sun and that gets converted to heat, which is uncomfortable for people with rosacea,” Dr. Sheu said. 

For people with acne issue, she recommends oil-free sunscreens that do not block the pores. If the person has sensitive skin, they should find an oil-free sunscreen that has zinc oxide or titanium dioxide. 


Suncare for kids 

As schools have broken up for the summer, it’s likely children in Cayman will be spending more time outdoors and on the beaches, being exposed to the sun’s dangerous ultraviolet rays. 

Dr. Sheu said parents should ensure their children are wearing plenty of sunscreen, which must be reapplied every two hours, and more often if they’re in and out of the water. 

“Stick with titanium dioxide and zinc oxide sunblocks, which do better for sensitive young skin,” she said. She also advised that children should wear hats and clothing like rash guards to protect their skin if they’re spending time on the beach and in the water. 

“It’s important to choose a sunscreen that blocks both UVA and UVB rays – a broad spectrum brand,” she said. Look for sunscreens that say “broad spectrum” on the label. 

While most sunscreens protect against UVB rays, which cause sunburn, there are some that do not block UVA rays, which do not cause sunburn but can increase the rate of skin cancer. Dr. Sheu said it was essential to opt for a brand that protects against both types of rays. 


Skin cancer 

Dr. Sheu advised that even people who have had skin cancer scares can still enjoy the sunshine and don’t need to hide indoors, so long as they are careful.  

“If someone has had a skin cancer, they should wear a hat, they should sit under an umbrella and in the shade if available. There are a lot of manufacturers who make quite fashionable sun protection clothing. It’s come beyond rash guards,” she said. 

Spray vs. cream 

Spray sunscreens have been growing in popularity due to the ease of use, but Dr. Sheu warned that people need to be mindful of applying the spray correctly if they want to ensure they are protected against ultraviolet rays. 

“People like using sprays because they are so convenient. The main thing about those is that you have to hold the nozzle closer to the skin in order for it to not be blown away by the wind,” she said, adding that if one holds the bottle a foot or more away from the skin, most of the spray ends up in the air. 

The ultimate advice for anyone who is exposed to sunlight is to wear sunscreen every day, reapply it regularly if you’re spending a lot of time outdoors, choose a high factor protection, wear a hat and don’t forget your sunglasses. 


Some simple steps can help you protect your skin during the long summer months. – PHOTO: FILE