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What is the Difference Between UVA and UVB Rays?

Learn about the differences between UVA and UVB rays and their effects on skin, and discover formulas to protect skin from the damaging effects of ultraviolet radiation.

Article Overview

  • UVA rays are longer than UVB rays and penetrate deeper into the skin, causing long-term damage like premature aging and wrinkles.

  • UVB rays are shorter and primarily affect the outer layers of the skin, causing sunburns and contributing to the development of skin cancer.

The light we see (and can't), electromagnetic waves, and radiation are all the same physical phenomenon: electromagnetic energy. This energy fills our indoor and outdoor environments in the form of radio and microwaves (measured by frequency in hertz), infrared and visible light (measured by wavelength in meters), and x-rays and gamma rays (measured by energy in electron volts).

If you’re wondering what this has to do with your skin, ultraviolet (i.e. UVA and UVB) rays likely ring a bell. Although these rays only account for 5% of the sun’s radiation that reaches the Earth’s surface, their short- and long-term impact makes them a central part of any conversation about skin health.


All UV rays are not created equal, which is why it’s important to understand UVA vs. UVB rays—and the effects that each of these electromagnetic energies have on the skin. (For the record, there are also UVC rays, but these are usually blocked by the Earth’s ozone layer.)

Ultraviolet A (UVA) Rays

  • Wavelength: 315-400 nanometers (nm)
  • Comprise 95% of the sun’s UV radiation that reaches the Earth’s surface
  • 30 to 50 times more prevalent than UVB rays
  • Strong and consistent year-round
  • Penetrate clouds and glass
  • Reach the dermal level where they damage collagen and elastin

Ultraviolet B (UVB Rays)

  • Wavelength: 280-315 nanometers (nm)
  • Comprise 5% of the sun’s UV radiation that reaches the Earth’s surface
  • Strength can depend on time of day, season, and location
  • Cannot penetrate glass
  • Only penetrate the epidermis, which is the upper layer of the skin

UVA vs. UVB Rays: Comparing Their Impact on the Skin

There’s a simple way to understand the difference between UVA and UVB rays. UVA rays are “aging” rays, and they are the main cause of sun damage and extrinsic (or external) skin aging. Think of UVB rays as “burning” rays because they lead to skin reddening, sunburn, and even blistering in severe cases—which is a significant risk factor for skin cancer.

Unlike UVB rays that cause sunburn, UVA rays are painless. When you compare UVA vs. UVB rays, UVA rays penetrate deeper into the skin and generate free radicals that can cause long-term damage that may ultimately appear as wrinkles, loss of elasticity, dark spots, and discoloration.

However, there is no difference between UVA and UVB rays when it comes to increased risk of skin cancer. All ultraviolet rays damage DNA within the skin cells that can potentially lead to mutations.

How to protect skin from UVA rays vs. UVB rays

Sunscreen labels can be confusing. Effective sun-protection products must filter out UVA and UVB rays, which is why it’s imperative to choose products that are labeled “broad spectrum.” It’s also important to understand that SPF only indicates a sunscreen’s level of protection against UVB rays. While some skin tones tan easily, those that are more prone to sunburn may require a higher SPF.

Corrective moisturizers

Skinceuticals Sunscreens for UVA vs. UVB Protection

We are committed to healthy skin today, tomorrow, and for years to come, which is why we offer mineral- and chemical-based broad-spectrum sunscreens with SPF 30 and higher.

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Physical Fusion UV Defense Sunscreen SPF 50: This lightweight tinted fluid provides 100%-mineral protection for all skin types. Its iron oxide color spheres instantly boost skin radiance and provide a universal tint that enhances most skin tones.

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Sheer Physical UV Defense Sunscreen SPF 50: Offering ultra-sheer mineral-based protection and a weightless matte finish for all skin types (including sensitive), this artemia salina-infused formulation spreads easily and dries quickly without leaving any residue behind.

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Physical Matte UV Defense Sunscreen SPF 50: Appropriate for oily and acne-prone skin as well as those who prefer long-lasting matte finish, this tinted sunscreen features an oil-absorbing mousse-like texture that helps smooth skin texture and minimize the appearance of pores.

Proper Sunscreen Application

To get the level of sun protection stated on any sunscreen label, it’s imperative to apply it correctly. First and foremost, apply an even layer to the face, neck, and chest 15 minutes before sun exposure (and before applying makeup). Most people don’t apply enough sunscreen, and a nickel-sized dollop should be used for the face alone. Three tablespoons (or the equivalent of a shot glass of sunscreen are recommended to protect exposed skin on the face and body. Also be sure to reapply sunscreen at least every two hours, as well as after swimming, sweating, and drying off with a towel.

Unique skin types, skin tones, and lifestyles can require different sunscreen formulations that provide broad-spectrum protection despite the difference between UVA and UVB rays. To find the ideal sun protection, use our online Routine Finder, visit one of our SkinCeuticals SkinLab locations, or schedule an appointment with a SkinCeuticals Skincare Professional for a one-on-one consultation.

Next: What are Environmental Aggressors?

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