SPF Sunblock Information

Sunblock or sunscreen is a lotion, spray or gel that contains one or more UV filters that reflect the sun's ultraviolet radiation from the skin. The first sunscreen was developed by chemist Franz Greiter in 1938 and in 1962 he introduced the standard measuring concept, Sun Protection Factor (SPF).

Type

SPF is used worldwide to measure, from 1 to 100, the effectiveness and the protection of the sunscreen against UV rays. The SPF number is the amount of UV radiation needed for the skin to get burned with the sunscreen on divided by the amount required without the sunscreen.

Identification

SPF numbers multiplied by 10 indicate the number of minutes the sunscreen will protect against the UV rays; after that time, another application will be needed. For example, an SPF 30 sunscreen will block out the sun for 300 minutes, or five hours.

Application

It is recommended that you apply sunscreen at least 20 minutes before going out. Although the SPF number indicates how long you can stay out in the sun, there are many other factors to take into consideration, such as time of day; your skin type; the amount of sunscreen applied and frequency; and activities you engage in---for example, swimming and toweling off will rub off most of the sunscreen.

Misconceptions

The American Academy of Dermatology advises wearing a broad-spectrum sunblock with at least SPF 15 on all sun-exposed areas; reapply every two hours. Generally, the higher SPF number, the better the protection. However, there is minimal difference between SPF 45 and SPF 100.

Previously, sunscreens have only protected against UVB rays---the type of rays that produce sunburn. However, UVA rays, which do not leave any visible traces, are in fact far more dangerous since they cause cell damages deep within the skin and increase the risk of malignant melanoma. Recently, sunscreens that protect against both UVB and UVA rays have become widely available.

Conclusion

When purchasing sunscreen, be sure to take note of the SPF level and use a decent amount before going out. Sunblock should always be used, even on cloudy days. Finally, sunscreen is usually applied to the face and body; however, many people forget to apply it to their ears, feet and lips. It is important to protect all exposed skin.

References

• How to Read Sunblock
• Confused by SPF? Take a Number; The New York Times; Catherine St. Louise; May 13, 2009

Resources

• Sun Protection and Sunscreen