Photoprotection - Importance and Strategies for Sun Protection

The recommended sun protection strategies are:

1) Adopt responsible behaviour.

2) Use photoprotective clothing and sunglasses.

3) Apply long-spectrum sunscreens (SP).

1) Responsible sun exposure

The intensity of solar radiation is significantly influenced by the time of day, season, weather conditions, altitude, latitude, reflective surfaces, among others.

Adopting correct behaviour is the best way to prevent skin damage caused by the sun. These include:

• Start sun exposure gradually and always avoid peak hours, i.e. between 11am and 5pm.

• Do not stay in the sun for prolonged periods and use the shade to protect yourself.

• Use PS with a sun protection factor (SPF) suitable for the type of skin, preferably equal to or greater than 30.

• Extreme caution should be exercised when exposing young children to the sun. Children under six months of age should not be exposed to the sun, and the use of hats, protective clothing and staying in the shade is recommended, but not the use of sunscreen.

• For older children a PS can be applied, preferably with a physical filter, and direct exposure of children under three years of age should be avoided.

• Increase your intake of water or sugar-free natural juices.

• Avoid exposure to the sun if you are taking medication that can cause photosensitivity reactions.
  
  

2) Use of photoprotective clothing and sunglasses

When outdoors, clothing should be worn to avoid direct exposure of the skin to the sun, particularly during peak hours. Clothing provides protection against UVA and UVB rays, with the added advantage of not causing allergies or skin irritation.

Loose-fitting clothes provide better sun protection than tight-fitting ones, and UV protection is higher for darker-coloured materials as they absorb more radiation. There are also fabrics treated with solar filters. 

Hats are a very important protective element. They should have a wide brim, at 360°, in order to protect also the face, the eyes, the neck and the ears; those with a specific brim for the neck provide even more protection.

Sunglasses protect the skin, eyes and eyelids, preventing the development of changes such as cataracts, photokeratitis and possibly retinal melanomas and age-related macular degeneration.

Glasses should filter UVA and UVB radiation and preferably have a lateral band, to avoid the passage of radiation through the sides.

Darker lenses do not necessarily confer greater UV protection, and may cause dilation of the pupil and greater arrival of radiation to the retina. Orange or yellow lenses provide the best protection against UV and visible blue radiation.

3) Use of sunscreens

Sunscreens (SP) are cosmetic products intended to be put on the skin with the primary purpose of protecting it from UV radiation by absorption and/or reflection. They were originally developed to prevent skin burns due to sun exposure. When applied correctly, they are effective in preventing sunburn, but also in reducing some chronic effects of UV radiation, including immunosuppression, photocarcinogenesis and photoaging.

SP should be broad-spectrum products protecting against UVA and UVB radiation and, if possible, blue visible light; they should also be hypoallergenic and non-comedogenic.

Their use is necessary all year round, even during cold seasons, especially when UV radiation can be amplified by altitude or reflection on ice, snow or water, e.g. during winter sports. 

A) Sunscreen types:

UV filters are substances contained in PS specifically intended to reflect and/or absorb radiation of certain wavelengths, in order to reduce skin exposure to such radiation. They can be of chemical (organic) or physical (inorganic) type, and many products combine substances of different types to maximise protection.

Organic filters absorb UV radiation and convert it into heat.

Physical filters are substances of mineral origin which act by scattering UV radiation. The substances used are metallic oxides, such as zinc oxide (ZnO) and titanium dioxide (TiO2). They are photostable and their allergenic potential is very low, which is why they are recommended for children and allergic individuals.

B) Correct use of sunscreens

The effectiveness of a PS is highly dependent on its correct application:

• PS should be applied generously and evenly, 15 to 30 minutes before sun exposure.

• To ensure the indicated protection, it is necessary to apply at least 2 mg/cm2 of PS, which is equivalent to about 36 g of the product, approximately 6 teaspoons.

• To remain effective, they must be reapplied frequently, at least every 2 hours, but also after bathing or if perspiration occurs, even for products that claim to be water-resistant.

• The PS chosen must be suitable for the skin phototype.

• The use of products containing both PS and insect repellent is not recommended, as PS generally has to be reapplied more frequently.

• In case concomitant use of insect repellent and PS is necessary, the latter should be applied before the repellent.

• It is important to pay attention to the expiry date and/or the period of use of the SP, and those which present changes in appearance or smell after some time of use should not be used. The package should be tightly closed after each use. It should not be exposed to great variations in temperature, heat sources or direct sunlight.
  
  

Sources
MSDmanuals
Mayo Clinic

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