SUN AND RADIATION

Inexhaustible source of energy and life, the sun is related with the most carefree and happy time of year, the summer. The beneficial effect of solar radiation on the human psyche is also known. Without overlooking the unique benefits of sunshine for the overall well-being - provided that sun exposure is rational and controlled - we need to emphasize that the sun poses several risks in cases of prolonged exposure. The most common effect of solar radiation on the skin is redness. 

Excessive and chronic exposure may have serious health effects, e.g., premature skin aging, even skin cancer. Depending on skin type and other factors, the exposure time, in which ultraviolet radiation can cause the serious aforementioned situations, differs from one person to another. The types of radiation, depending on wavelength, are divided into:

• UVΑ (320-400nm)
• UVB (290-320nm)
• UVC (100-290nm)

UVA radiation penetrates deeper into the skin than UVB, while its action is continuous throughout the day and year. The UVA rays are responsible for premature skin aging, while long-term exposure -especially since childhood - can lead to skin cancer.

UVB radiation is most intense during summer months, with the intensity peaking during early afternoon. UVB rays contribute to the creation of vitamin D and their action is limited to the skin surface, activating the melanocytes that produce melanin. UVB radiation is responsible for burns and rashes on the skin caused by sun exposure. Chronic exposure to this type of ultraviolet radiation can also lead to skin cancer. 

UVC radiation is the most threatening kind. However, it is absorbed by the ozone layers and thus does not reach the earth's surface. 


 
*Chorium = Dermis

The Sun Protection Factor or SPF -as it is internationally known- indicates the degree of protection provided by a sunscreen product, against UVB radiation.
Without protection, sun exposure is safe only within a specific time limit, which, according to skin type and natural resistance, varies from 5 to 30 minutes. The multiplication of a product's Sun Protection Factor (SPF) by the skin's natural sun resistance span (with no protection) produces the total amount of time, during which we can safely enjoy the sun.

Here is a simple example: Suppose your skin starts getting red naturally, without sunscreen, after being sun exposed for 20 minutes. If you choose a sunscreen with a factor of 10 (SPF 10), your skin will develop the same redness after 20 minutes x 10. In essence, after 200 minutes.
Nonetheless, sunscreen application should be repeated regularly, after swimming, toweling and perspiring.

As already pointed out, the SPF provides protection against UVB and not UVA radiation.

• UVA protection assessment is conducted through laboratory measurements (in vitro), which calculates the protection index in connection to the SPF (protection from UVB radiation), it can also be measured in vivo (on volunteers).
• In order to achieve effective protection against both types of radiation (UVA & UVB), the index used to measure the UVA radiation coverage protection UVA, has to be equivalent to at least 1 / 3 of the SPF*.

In other words, if a product has a Sun Protection Factor of 30 on radiation UVB, the respective index for UVA radiation should be at least 10.
Chart of available factors and levels of protection, based on the SPF *:


SUN PROTECTION FACTOR (SPF)


LEVEL OF PROTECTION

6, 10


Low

15, 20, 25


Medium

30, 50


High

50+


Very High


TIPS FOR THE FIRST DAYS OF EXPOSURE TO THE SUN


Sun exposure should not exceed 30 minutes, the first few days, if you want to avoid sunburn. Slow tanning is better, lasts longer and it is safer, health wise.

• If you have light/very light skin, the initial sun exposure time should be about 15-30 minutes. The duration can be increased by 10 minutes, every two days of continuous exposure.

• If you have fair skin, usually with freckles, that gets sunburned almost always and never tans, experts recommend an SPF 50/SPF 50+ sunscreen, for the first few days of sun exposure.

• If you have medium skin, the initial sun exposure time should be about one hour and can be increased by 20-30 minutes, every two days of continuous exposure.

• If you have skin that burns occasionally and tans easily, usually brown hair and eyes, Mediterranean skin type, experts recommend, initially, an SPF 20-30 sunscreen.

• If you have dark - brown skin that never burns and tans very easily, experts recommend an SPF 15 sunscreen, for the first few days of sun exposure.

Once you are tanned enough, you can switch to a lower SPF –always ensuring your protection- to achieve an even deeper tan result.
All the above apply provided you avoid exposure to solar radiation between 11:00 am – 3:00 pm and wear the appropriate SPF for your skin type.