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06 Jun 2023

SUMMARY: When it comes to sun protection, one of the most commonly asked questions is “What is the difference between UVA vs UVB rays?” UVA (aging) rays can cause premature skin aging such as wrinkles and age spots, while UVB (burning) rays are responsible for tanning and sunburn—yet exposure to both can increase your risk of skin cancer. Effective sun protection products must filter out UVA and UVB rays, and it’s important to understand the terms you see on your sunscreen. The SPF rating indicates the level of protection against UVB rays, and the term “broad spectrum” indicates that a product helps shield the skin from UVA rays as well. Some sun protection products may also include antioxidants, which can help further prevent environmental skin damage.


UV rays, or ultraviolet rays, only account for 5% of the sun rays that reach the earth1, but they are very powerful. There are several kinds. While UVC rays are usually blocked by the ozone layer, UVA and UVB rays reach the Earth’s surface and can have an effect on unprotected skin.

UVA: A factor responsible for premature extrinsic skin aging (think UVA for aging)
Ultraviolet A rays have a longer wavelength than UVB rays and are often associated with the signs of premature skin aging. Present throughout the year, from sunrise to sunset, and even on cloudy days, UVA rays account for about 95% of the ultraviolet rays that reach the Earth's surface2. These rays can penetrate clouds, glass, and through the epidermis into the dermis of your skin. Unlike UVB rays that cause sunburn, UVA rays are painless—but they are far from harmless. UVA rays can reach the cells in the deeper layers of the skin and produce free radicals that can contribute to long-term damage such as3:
  • Photoaging: When the skin’s supportive structure (which is comprised of collagen and elastin fibers) is compromised, this results in wrinkles and loss of elasticity.
  • Dark spots and discoloration: UVA rays play a role in conglomeration of melanocytes, which may lead to formation of age spots and excessive pigmentation of melasma.
  • Development of skin cancer. Learn more about what causes skin cancer and how you can help minimize the risk of getting it.
UVB: A factor responsible for sun burning (think UVB for burning)
Ultraviolet B rays have shorter wavelengths than UVA rays, and are associated with skin burning (sunburn). UVB rays make up just about 5% of the UV rays that reach the Earth4 and are strongest during the summer, especially from 10am to 2pm. Unlike UVA rays, UVB rays cannot penetrate clouds and glass, but they can penetrate into the epidermis. These rays are responsible for tanning, sunburn, and skin cancer.


UVA protection
UVA protection may not have a number-based rating system, but the term “broad spectrum” indicates that a sunscreen shields the skin from UVA rays & UVB rays. As with UVB protection, it’s imperative to apply the proper amount of sunscreen to protect against UVA damage.

UVB protection and SPF
UVB protection is measured using a system called SPF, which stands for sun protection factor. This is relative to the amount of time that a sunscreen will protect you.

For example: let’s assume that you can normally stay in the sun for 10 minutes before burning. If you apply an SPF of 15, the time it takes to burn is multiplied by the sun protection factor of 15. Theoretically, in this example, you will be able to stay in the sun 10 x 15 = 150 minutes before burning. However, it is important to remember that factors like sweating or swimming will impact the efficacy of any sunscreen, so it is important to reapply every 2 hours or more frequently.

In addition, to achieve this level of protection, it’s essential to apply a generous, even layer of sunscreen, which is likely more than you think. A shot glass amount is generally recommended for adequately covering the entire body5. The FDA recommends that you apply SPF 15 at minimum6, as it is able to block 93% of UVB rays7.


Everyone's skin is affected by the sun, but skin may react differently to sun exposure depending on the level of melanin found in skin. Lighter skin tends to sunburn more easily than darker skin. It is important to understand how your skin reacts to sun exposure when selecting a sunscreen. Dry skin may need a specific type of sunscreen that contains moisturizing ingredients to prevent further dryness.

What is my Fitzpatrick skin type?
The Fitzpatrick skin type system classifies skin type based on how much pigment is found in your skin and how your skin reacts to the sun8. There are six types:
  • Type I: Pale skin (especially those with red hair), always burns, never tans, many freckles.
  • Type II: Fair skin, always burns, sometimes achieves a slight tan, freckles.
  • Type III: Fair to light brown skin, sometimes burns, always tans (medium tan), some freckles.
  • Type IV: Medium to dark and olive skin, rarely burns, always tans (dark tan), no freckles.
  • Type V: Brown skin, rarely burns, always tans (very dark tan), no freckles.
  • Type VI: Black skin, never burns, no freckles.


Not all sunscreens are created equal. When selecting a sunscreen, dermatologists recommend checking the label for these 3 characteristics:

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Protecting the skin against UVA and UVB rays is essential. Educate yourself on the basics of sun protection that are vital for maintaining healthy skin and minimizing the risk of skin cancer.

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