Sunlight contains ultraviolet (UV) radiation, which consists of different types of rays. The types of UV radiation you’re probably most familiar with are UVA and UVB rays. These rays can affect your skin in different ways.
In this article, we’ll take a closer look at the key differences between UVA and UVB rays, how they affect your skin, and what you can do to limit sun damage.
UV radiation is a form of electromagnetic energy. It can come from natural sources, such as sunlight, as well as artificial sources, such as lasers, black lights, and tanning beds.
The sun is the most significant source of UV radiation. It’s the product of a nuclear reaction at the sun’s core, and the radiation travels to earth via the sun’s rays.
UV rays are classified according to wavelength: UVA (longest wavelength), UVB (medium wavelength), and UVC (shortest wavelength).
Here’s a quick comparison of the three main types of UV rays.
| UVA | UVB | UVC | |
|---|---|---|---|
| Energy level | lowest | medium | highest |
| Skin cells affected | inner cells in the top layer of skin, including dermis | cells in the top layer of skin | outermost cells in the top layer of skin |
| Short-term effects | immediate tanning, sunburn | delayed tanning, sunburn, blistering | redness, ulcers and lesions, severe burns |
| Long-term effects | premature aging, wrinkles, some skin cancers | skin cancer, can contribute to premature aging | skin cancer, premature aging |
| Source | sunlight, tanning beds | sunlight, tanning beds | UVC lights, mercury lamps, welding torches |
| % of the sun’s UV rays | ~95 | ~5 | 0 (filtered out by the atmosphere) |
Here are some important facts about ultraviolet A (UVA) rays and how they affect your skin.
- They have higher wavelengths, but lower energy levels than other UV rays.
- They’re more penetrating than UVB rays, which means they can affect cells deeper in the skin.
- They cause indirect damage to DNA.
- They cause skin to age prematurely, leading to visible effects such as wrinkles. They’re also associated with some skin cancers.
- Unlike UVB rays, they’re not absorbed by the ozone layer. About
95 percent of the UV rays that reach the ground are UVA rays. - They cause an immediate tanning effect, and sometimes a sunburn. The effects of UVA rays tend to appear right away.
- UVA rays are the main type of light used in tanning beds.
- They can penetrate windows and clouds.
Here are some important facts about ultraviolet B (UVB) rays and how they affect your skin.
- Relative to UVA rays, UVB rays have shorter wavelengths and higher energy levels.
- UVB rays damage the outermost layers of the skin.
- They directly damage DNA.
- UVB rays cause most skin cancers, but they can also contribute to skin aging prematurely.
- They’re partially absorbed by the ozone layer, but some rays still get through. About
5 percent of the UV rays that reach the ground are UVB rays. - Overexposure to UVB rays leads to sunburns. Usually, the effects of UVB rays are delayed, or appear a few hours after sun exposure.
- Most tanning beds use a combination of UVA and UVB rays. Special UVB-only tanning beds may be touted as safe, but they still cause skin damage. No tanning beds are safe to use or recommended.
- They don’t penetrate windows, and are more likely to be filtered by clouds.
Ultraviolet C (UVC) rays have the shortest wavelengths and highest energy levels of the three types of UV rays. As a result, they can cause serious damage to all life forms.
Fortunately, UVC radiation is completely filtered out by the ozone layer. As a result, these rays from the sun never reach the ground.
Man-made sources of UVC include welding torches, special bacteria-killing light bulbs, and mercury lamps.
Although not considered a risk for skin cancer, UVC rays can cause severe damage to human eyes and skin, including burns, lesions, and ulcers on the skin.
A number of environmental factors can affect when UV rays are the most powerful. Some of these factors include:
Time of day
UV exposure is highest between 10 a.m. and 4 p.m. During this daily window, the sun’s rays have less distance to cover. This makes them more powerful.
Season
UV exposure is highest in the spring and summer months. During these seasons, the sun is at a higher angle, which increases UV ray intensity. However, the sun can still affect you during fall and winter.
Latitude
UV exposure is highest in areas on or near the equator, where UV rays have less distance to travel before reaching the ground.
Altitude
UV rays are more powerful at higher elevations because they have less distance to travel.
Ozone
The ozone layer provides protection from UV rays. But greenhouse gases and pollutants have caused the ozone layer to thin, increasing UV intensity.
Clouds
Clouds filter out some UV rays from reaching the ground. However, it depends on the type of cloud. Dark, water-filled clouds may block out more UV rays than high, thin clouds.
Reflection
UV rays reflect off surfaces such as snow, water, sand, and pavement. This can increase UV exposure.
To keep your skin healthy, it’s important to protect yourself from the sun’s rays, especially if you know you’re going to be outdoors for a length of time.
Consider the following tips to limit sunburn, premature aging, and DNA damage:
Apply sunscreen
Choose sunscreen that offers broad-spectrum protection. This means the sunscreen has the ability to block out both UVA and UVB rays.
A higher sun protection factor (SPF) will provide more protection, but remember that no sunscreen is 100 percent effective at blocking out UV rays. The American Academy of Dermatology (AAD) recommends using a sunscreen that’s 30 SPF or higher.
Sunscreen needs to be reapplied at least every 2 hours or more frequently if you’re sweating, exercising, or swimming. It’s important to know there are no waterproof sunscreens, only those that are water-resistant.
When shopping for sunscreen, you may want to opt for a physical, or mineral-based, product. Recent research has found that the ingredients in some chemical sunscreens can be absorbed into your blood.
At this time, only two sunscreen ingredients — zinc oxide and titanium dioxide — are “generally recognized as safe and effective” (GRASE) by the Food and Drug Administration (FDA). These ingredients are found in physical sunscreens.
Cover up
Clothes can provide some protection from UV exposure. Tightly-woven dry fabrics are best. Many outdoor companies make clothes that provide increased protection from UV rays.
Stay in the shade
Limit your exposure to direct sunlight by staying in the shade. This is most important between 10 a.m. and 4 p.m., when UV rays are stronger.
Wear a hat
A wide-brimmed hat can provide additional protection to your ears and neck.
Wear sunglasses
Choose sunglasses that offer UV protection to prevent damage to your eyes and the surrounding skin.
The sun is one source of vitamin D, which is why it’s sometimes called the “sunshine vitamin.”
However, the AAD advises against getting vitamin D from sun exposure or tanning beds, as UV rays can cause skin cancer.
Rather, they recommend following a healthy diet that includes foods that are natural sources of vitamin D. These include fatty fish like salmon, tuna, sardines, and mackerel.
Vitamin D is also found in maitake mushrooms, egg yolks, and foods and drinks that are fortified with vitamin D, like some milks, breakfast cereals, and orange juice. You may also want to consider taking vitamin D supplements.
Both UVA and UVB rays are capable of damaging your skin.
UVA rays can penetrate your skin more deeply and cause your skin cells to age prematurely. About 95 percent of the UV rays that reach the ground are UVA rays.
The other 5 percent of UV rays are UVB. They have higher energy levels than UVA rays, and typically damage the outermost layers of your skin, causing sunburn. These rays directly damage DNA and are the cause of most skin cancers.
FAQs
UVA vs. UVB Rays: What’s the Difference? ›
Ultraviolet A (UVA) has a longer wavelength. It is associated with
UVA rays have a lower amount of energy and a longer wavelength than UVB rays. They can enter the middle layer of your skin called the dermis. UVA rays form 95% of the UV radiation which reaches the earth. They have a role to play in the formation of some types of skin cancers.
Which is better UVA or UVB? ›UVA rays can penetrate your skin more deeply and cause your skin cells to age prematurely. About 95 percent of the UV rays that reach the ground are UVA rays. The other 5 percent of UV rays are UVB. They have higher energy levels than UVA rays, and typically damage the outermost layers of your skin, causing sunburn.
Is vitamin D from UVA or UVB? ›When your skin is exposed to sunlight, it manufactures vitamin D. The sun's ultraviolet B (UVB) rays interact with a protein called 7-DHC in the skin, converting it into vitamin D3, the active form of vitamin D.
Does UVA or UVB make you darker? ›How Tanning Happens. The sun's rays contain two types of ultraviolet radiation that reach your skin: UVA and UVB. UVB radiation burns the upper layers of skin (the epidermis), causing sunburns. UVA radiation is what makes people tan.
Which is more harmful UVA or UVB? ›UVA rays, while slightly less intense than UVB, penetrate your skin more deeply. Exposure causes genetic damage to cells on the innermost part of your top layer of skin, where most skin cancers occur. The skin tries to prevent further damage by darkening, resulting in a tan.
Are UVB rays more harmful than UVA? ›UVB radiation makes up only 5% of the UV rays from the sun, but it is very high energy. “UVB does not penetrate as deeply as UVA, but it can wreak havoc on the top layers of your skin.” George says. UVB damages skin cells and causes DNA mutations that can eventually lead to melanoma and other types of skin cancer.
Does UVA or UVB cause skin damage? ›UVA rays are mainly linked to long-term skin damage such as wrinkles, but they are also thought to play a role in some skin cancers. UVB rays have slightly more energy than UVA rays. They can damage the DNA in skin cells directly, and are the main rays that cause sunburns.
Which UV rays are harmful? ›Short-wavelength UVC is the most damaging type of UV radiation. However, it is completely filtered by the atmosphere and does not reach the earth's surface. Medium-wavelength UVB is very biologically active but cannot penetrate beyond the superficial skin layers.
Do I need UVA and UVB protection? ›It's important to protect your skin from both types: UVB rays cause sunburn and play a key role in developing skin cancer. A sunscreen's SPF number refers mainly to the amount of UVB protection it provides. UVA rays cause skin damage that leads to tanning as well as skin aging and wrinkles.
What vitamin is made from UVB rays? ›
Vitamin D is the sunshine vitamin that has been produced on this earth for more than 500 million years. During exposure to sunlight 7-dehydrocholesterol in the skin absorbs UV B radiation and is converted to previtamin D3 which in turn isomerizes into vitamin D3.
Can you get vitamin D from the sun through clothes? ›It is obtained through eating certain foods and is also synthesized by the body when the skin is exposed to the sun's UV rays. However, this reaction is blocked by clothing, increasing your risk of deficiency and the associated health implications.
Does UVA destroy vitamin D? ›The UVA dose does not influence 25(OH)D levels under short exposure times. However, there was a significantly lower increase of 25(OH)D levels during longer UVA irradiation (≥9 min).
Is melanoma caused by UVA or UVB rays? ›Both UVB and UVA have been shown to induce melanoma in mice. UVB radiation has a well-established role in melanomagenesis, but UVA's contribution is controversial.
What makes you tan quicker? ›Apply a sunbed cream or tanning accelerator prior tanning
There is a great number of sunbed creams, varying from moisturisers and coolers to bronzers and creams with tingle factors. All these products are specifically formulated in a way that enables you to tan faster and get a darker colour.
Exposure to UV radiation increases the pigment melanin in your skin. UVA radiation triggers the release of melanin within the skin itself, while UVB radiation stimulates your body to produce more melanin, resulting in a sun tan. Both of these types of UV radiation are present in the sun's rays.
What is the difference between UVA and UVB quizlet? ›UVA: is the longest wavelength ultraviolet light and is responsible for the actual darkening of the skin. UVB: is the middle wavelength of ultraviolet light. Exposure to UVB is necessary to stimulate the production of melanin cells in the skin. UVC: is the shortest, most dangerous wavelength of ultraviolet light.
What is the difference between UVA and UVB rays in terms of their wavelength? ›Approximately 90% of UV radiation reaching the Earth's surface. UVA is again divided into UVA-I (340 nm - 400 nm) and UVA-II (315 nm - 340 nm). UVB – Medium-wavelength UVB covers the range 280–315 nm. Approximately 10% of UV radiation reaching the Earth's surface.
What's the difference between UVA and UVB for reptiles? ›UVA light helps regulate behaviors such as feeding, diurnal movement, mating and similar activities. UVB light allows the synthesis of vitamin D3, which helps to absorb calcium. UVC light is not required for reptiles, but it can help kill bacteria.
What is difference between UVA and UVB wavelength? ›The UV region covers the wavelength range 100-400 nm and is divided into three bands: UVA (315-400 nm) UVB (280-315 nm)