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To limit the harmful effects of UV rays on the body, it is important to choose a suitable sunscreen, when choosing a sunscreen, it is necessary to pay attention to the SPF and PA numbers on the sunscreen.1. UV rays and the effects of UV rays on the body
UV rays, also known as ultraviolet rays or ultraviolet rays, are rays of low wavelength, high frequency and invisible to the naked eye.UV rays include three types A, B and C. This division is based on the wavelength of the rays.
UV C rays are the rays with the highest energy, the smallest wavelengths that cause the most harm to the body, but due to the absorption of the ozone layer, almost all UV C rays are blocked. UVB rays (wavelength 280 - 315 nm) account for 5%. UVA rays (315 - 380 nm) account for 95% of ultraviolet rays reaching the earth Benefits of UV rays:
UV rays work to help the body synthesize vitamin D, fight rickets, cure some skin diseases.. With a moderate dose UV rays stimulate all activities of the body. However, if the intensity is high and frequent exposure to UV rays can be harmful to the body. Harmful effects of ultraviolet rays on the body:
Skin aging, changes in the DNA of skin cells have the risk of causing skin cancer, melanoma. Causes sunstroke, black skin, melasma and freckles. Affects the eyes when in direct contact with the eyes, mildly causing temporary loss of vision after a period of self-limiting, more severe causes retinal failure, cataracts and may cause complete vision loss. Sun exposure for a long time can cause nervous depression, depression... by absorbing a lot of UV rays
Nắng nóng chứa nhiều tia UV có hại cho sức khỏe
2. What are the SPF and PA numbers on sunscreens?
To avoid the effects of UV rays on the body, it is important to choose a sunscreen that is suitable and has UV protection. To know the ability of sunscreen to protect against UV rays, people rely on SPF and PA numbers.2.1. What is SPF? SPF (sun protection factor) is a measure of the protection against UV rays used in sunscreens. This norm is calculated according to the number of hours and percentage when applying sunscreen on the skin. The minimum SPF in sunscreen is 15 and the highest is 100. According to international standards, 1 SPF is capable of protecting skin and limiting the harmful effects of UV rays for about 10 minutes. Specifically:
Sunscreen with an SPF of 15 will protect the stomach within 150 minutes. Sunscreen with an SPF of 50 will protect the stomach for 500 minutes. How to read and understand the SPF index and the meaning of the SPF index: The SPF index is understood in two ways as follows:
Over time: That is, multiply the SPF index by 10 to calculate the time to protect the skin against the harmful effects of rays. UVB in minutes. For example, a sunscreen with an SPF of 30 will protect the skin from UVB rays for 300 minutes. Percentage: When placed in perfect conditions, a sunscreen with an SPF of 15 will block about 93.4% of UV damage, SPF 30 about 96.7%, SPF 50 about 98% . This ratio is also relative for a certain period of time.
Chỉ số SPF thường được ghi trên nhãn hộp kem chống nắng
How to read the PA index on sunscreen: Usually on the sunscreen packaging, the PA index is shown with the "+" sign, which is understood as follows:
PA+ has UVA protection at 40 -50%. PA++ has better UVA protection, at 60-70%. PA+++: has good UVA protection, up to 90%. PA++++: Has very good UVA protection, over 95%. However, for some sunscreens, the PA index may not be seen, but instead an abbreviation such as UVA-UVB, UVA/UVB or UVA1, UVA2. Or are the specific symbols of some brands and countries.. For example, SPF 60-12 means SPF 60 and PA+++.
The SPF number on the sunscreen indicates the body's ability to protect against the harmful effects of UVA and UVB rays on the body. Summer time, the amount of UV rays reaching the earth is the highest, causing a significant impact on the body. Using sunscreen is an effective way to avoid the harmful effects of UV rays.
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