A little bit of sun goes a long way. Though small amounts of invisible ultraviolet (UV) rays are essential for the production of vitamin D, prolonged exposure to the sun can result in early skin ageing, wrinkles, loss of skin elasticity, dark patches or age spots, skin cancer, cataracts and other problems.
Sunscreen plays a vital part in protecting you from the sun as it contains filters which reflect or absorb UV rays.
"Using a sunscreen will help reduce skin ageing as a result of sun exposure," said Dr Tan Kian Teo, a consultant dermatologist at Skin Physicians. "How much protective effect it has depends on the type of sunscreen, how it is used and the amount of sun exposure."
UVA AND UVB RAYS
A good sunscreen provides protection against two types of UV rays - UVA and UVB.
UVB tends to damage the skin's more superficial epidermal layers and is the chief cause of skin reddening and sunburn, which increases your chances of developing skin cancer.
UVA plays a big part in premature skin ageing. It penetrates the deeper skin layers, damaging connective tissue and blood vessels. The skin would gradually lose its elasticity and start to wrinkle.
Both types of UV rays can cause cancer.
CHEMICAL V PHYSICAL
There are physical sunscreens and chemical sunscreens, though most commercially available sunscreens contain both elements, said Dr Tan.
"A physical sunscreen blocks or deflects UV light while chemical sunscreen absorbs or scatters UV light," he explained.
While many physical sunscreens are thick and opaque, a chemical sunscreens are often colourless and, therefore, more cosmetically acceptable, dermatologists said.
"A physical sunscreen contains titanium dioxide and zinc oxide that physically reflect or scatter UV rays. However, it leaves a white residue and does not wash off easily," said Dr Suzanne Cheng, a consultant dermatologist at National Skin Centre.
Still, due to the development of micro-sized titanium dioxide and zinc oxide (which are extremely small nanoparticles), such a sunscreen has gained popularity in recent years because its smaller particles make it easier to apply and less visible on the skin, she said.
"Babies, pregnant women, children and people with sensitive skin can use inorganic or physical sunscreens which are chemical-free to reduce their risk of skin irritation and skin allergy," said Dr Chong Wei Sheng, a senior consultant dermatologist at National Skin Centre.
The titanium dioxide and zinc oxide found in physical sunscreens are minerals, which lie on top of the skin, shielding it from UV rays.
A chemical sunscreen, on the other hand, contains ingredients such as avobenzone and ecamsule, which absorb UV rays and convert them into energy. These chemicals are absorbed into the skin.
All physical sunscreens are effective as soon as they are applied, while chemical sunscreens should be applied on dry skin 30 minutes before sun exposure to allow the ingredients to bind to the skin.
You can find sunscreens in cream, gel, oils, lotions, sprays or even stick forms.
"In general, sunscreens for the body are thicker and may be oilier. However, some may be perfectly suited for both the face and the body. It really depends on the individual's skin type and the sunscreen," said Dr Tan.
There is some concern that sprays can produce toxic fumes. So, if you are using a spray, do not spray it directly on your face.
If your sunscreen has passed its expiration date, do not use it as it will not be as effective.
There are some concerns over a few sunscreen ingredients. One of them is oxybenzone, as research on animals showed that it might disrupt hormones.
Another one is retinyl palmitate, also known as vitamin A or retinol, which has been associated with skin cancer in mice, said Dr Tan.
Vitamin A is believed to slow skin ageing, but when used on skin exposed to sunlight, there is the possibility that it may speed up the growth of cancerous tumours. Some people have said that sunscreens with vitamin A should be avoided.
So far, however, there is no scientific evidence to show that these ingredients will harm humans, said Dr Tan, and they are still deemed safe by health authorities.
UV exposure generates free radicals, which are chemicals that can damage cells, However, the use of a sunscreen reduces the amount of free radicals that would otherwise be generated, said Dr Tan.
This article was published on May 8 in Mind Your Body, The Straits Times.Get a copy of Mind Your Body, The Straits Times or go to straitstimes.com for more stories.