Exposure to the sun has been associated with melanoma, non-melanoma skin cancers (basal cell and squamous cell carcinoma), and photo-aging (wrinkling, fragile skin, and spotty dyspigmentation (so called “liver spots”). Both melanoma and non-melanoma skin cancers are more common in those with light skin, light hair, and blue eyes, those who sunburn easily, suntan poorly, or freckle with sun exposure.
There is good evidence that the risk of both melanoma and non-melanoma skin cancers is increased with increased UV exposure, although they differ in the way that UV exposure causes them and this influences prevention. Non-melanoma skin cancers are most strongly related to lifelong chronic UV exposure, whereas melanoma correlates best with episodic UV exposure and blistering sunburns.
UVA & UVB
There are two forms of ultraviolet (UV) light to protect against: UVA and UVB. UVA is present throughout the entire day (not just the peak sun hours), and comes through glass and clouds. UVA plays a key role in skin wrinkling, leathering, and skin cancer promotion.
UVB are burning rays present in greatest amounts during midday. UVB rays play a major role in skin cancer promotion and photoaging.
The sun protection factor (SPF) number on the sunscreen lotion is a guide as to how long you can stay in the sun before risking sunburn. Recent studies have shown that most people apply sunscreens too thinly and therefore the SPF is probably less than what it says on the bottle.
“Waterproof” on the sunscreen label indicates that the protection is effective for four 20-minute swims. “Water resistant” is effective for two 20-minute swims. Reapply more frequently if perspiring excessively or toweling off frequently. Whichever form of sunscreen is chosen, it must be applied 20 to 30 minutes before being exposed to the sun. A new component of sunscreens, Parsol or Avobenzone, extends the protection from UVA and is advisable.
Choosing a sunscreen is an important part of your complete sun protection program but remember it is only one part! Sunscreens are typically divided into two broad categories: physical and chemical. Physical sunscreens such as titanium dioxide and zinc oxide actually reflect and scatter ultraviolet light, while chemical sunscreens act as protective filters by absorbing ultraviolet light.
Patients with sensitive skin may benefit from using sunscreens with no dyes or perfumes. Patients with acne or oily skin should use sunscreens that include “hypo-comedogenic or non-comedogenic” on the label. These words mean that this product will be less likely to clog skin pores and contribute to acne.
Types of Sunscreen Vehicles
- Oils: The most effective sunscreen ingredients are oil-based. They spread easily and have good water resistance. However, they are greasy and messy, cost more, and are easy to spread too thinly (which reduces their SPF).
- Emulsions: These are creams or lotions and are the most widely used sunscreen vehicles. They feel good and are easy to spread. The difference between creams and lotions depends on how much oil is used in the emulsion and therefore how viscous the product is.
- Ointments: These are unpopular because they are thick and greasy. Their use is restricted to activities involving prolonged water exposure such as surfing.
- Gels: The water-based gels do not feel greasy or occlusive and are popular with people with oily skin and those who are more physically active. They are difficult to apply uniformly and can be irritating. Alcohol-based gels are more water resistant but can sting, especially around the eyes.
- Sticks: Great for localized areas such as the nose and lips.
- Aerosolized Sunscreens: Usually oil based. Are easy to use but apply unevenly.
Recommendations for proper sun protection
- Apply before going out. It takes about 20 minutes for the active sunscreen ingredients to fully absorb into the skin.
- Apply enough (about one ounce for an adult body). The effectiveness of any sunscreen depends on the amount applied.
- Reapply frequently. Sunscreens become inactivated over time and they also get rubbed, sweated and washed away. Reapply every two hours and after swimming for maximum effect.
- Use a broad-spectrum and high SPF product of at least SPF 15 that contains both UVA and UVB.
- Don’t rely on sunscreen alone. Use sun protection such as hat, sunglasses with UV protection, long-sleeved clothing. Beware of reflectivity from sand, snow, cement and water. Utilize the shade.
- Don’t use sunscreen as an excuse to spend more time in the sun. Limit child’s UV exposure by decreasing time in the sun during peak sun hours (10 a.m. to 3 p.m.). Individualize interventions based on child’s skin color, susceptibility to burns, family history and presence of moles.
- Babies under six month sold should be kept out of direct sunlight and have adequate clothing for physical protection. Most recommend sunscreen for infants over six months. Selected use in younger infants is not harmful but should rarely be necessary because they should not be exposed to direct sunlight.