--- description: Understand the basics about UV radiation and how it damages your skin, learn about the UV index and how to protect against skin cancer. title: UV Radiation image: https://www.skincancer.org/wp-content/uploads/Beyond-the-sun.jpg --- [Home](https://www.skincancer.org/) › [Risk Factors](https://www.skincancer.org/risk-factors/) › UV Radiation # UV Radiation & Your Skin ## The Truth About Sun Damage When it comes to [skin cancer](http://skincancer.org/skin-cancer-information/), a major** risk factor** is prolonged exposure to **ultraviolet (UV) radiation** from the sun and tanning beds. Understanding UV radiation and how it damages your skin is an important first step in safeguarding yourself against skin cancer. The good news is that *you can* *greatly reduce* the danger posed by UV radiation. You can enjoy outdoor activities and limit your skin cancer risk by taking simple, smart [protective measures](http://skincancer.org/skin-cancer-prevention/). - [What is UV radiation?](#what) - [What is at stake?](#stake) - [What you need to know](#know) - [UVB facts and risks](#uvb) - [UVA facts and risks](#uva) - [Protect yourself](#protect) - [What is the UV Index?](#whatisuvindex) ### What is UV radiation? UV radiation is part of the natural energy produced by the sun. On the electromagnetic spectrum, UV light has shorter wavelengths than visible light, so your eyes can’t see UV, but your skin can feel it. Tanning beds also emit UV radiation. UV radiation is a proven human carcinogen. Two types of UV light are proven to contribute to the risk for skin cancer: - **Ultraviolet A** (UVA) has a longer wavelength. It is mainly associated with tanning and skin **aging** but can also lead to sunburn. - **Ultraviolet B** (UVB) has a shorter wavelength. It is mainly associated with sunburn, but also causes a delayed tanning response and contributes to skin aging **UVA and UVB rays make a dangerous team**. A sunscreen’s SPF number reflects both the amount of UVB and UVA protection it provides. It’s important to look for the words **broad spectrum** on a sunscreen product label, which means it has ingredients that can protect you from UVA as well as UVB rays. It’s crucial to protect your skin from *both*. **Bottom line**: While UVA and UVB rays differ in how they affect the skin, they both do harm. Unprotected exposure to UVA and UVB damages the DNA in skin cells, producing mutations that can lead to **skin cancer** and premature aging. UV rays can also cause [eye damage, including cataracts and eyelid skin cancers](http://skincancer.org/skin-cancer-prevention/sun-protection/eye-protection/). ### What is at stake? UV radiation is a proven human carcinogen, causing [basal cell carcinoma (BCC)](http://skincancer.org/skin-cancer-information/basal-cell-carcinoma/) and [squamous cell carcinoma (SCC).](http://skincancer.org/skin-cancer-information/squamous-cell-carcinoma/)  These types of cancers often appear on sun-exposed areas of skin. Fortunately, when discovered and treated early, these common skin cancers are usually curable. UV exposure that leads to [sunburn](http://skincancer.org/risk-factors/sunburn/) has proven to play a strong role in developing [melanoma](http://skincancer.org/skin-cancer-information/melanoma/), a dangerous type of skin cancer. Research shows that the UV rays that damage skin can also alter a gene that suppresses tumors, raising the risk of sun-damaged skin cells developing into skin cancer. ### What you need to know - **A majority of nonmelanoma skin cancers** (NMSC) and a large percentage of melanomas are associated with exposure to UV radiation from the sun. - **UV exposure is a powerful attack** on the skin, creating damage that can range from premature wrinkles to dangerous skin cancer. - **Damage from UV exposure is cumulative** and increases your skin cancer risk over time. While your body can repair some of the DNA damage in skin cells, it can’t repair all of it. The unrepaired damage builds up over time and triggers mutations that cause skin cells to multiply rapidly. That can lead to malignant tumors. - **The degree of damage** depends on the intensity of UV rays and the length of time your skin has been exposed without protection. Location is also a factor. [The UV Index](https://www.skincancer.org/blog/the-uv-index-know-your-risk/) measures the intensity of UV radiation at a specific location. If you live where the sun is strong year-round, your exposure level and risk increases. - **You can easily reduce** your likelihood of developing skin cancer by [protecting yourself](http://skincancer.org/skin-cancer-prevention/sun-protection/) against UV radiation. ### UVB facts and risks - **UVB** penetrates and damages the outermost layers of your skin. Overexposure causes [sunburn,](http://skincancer.org/risk-factors/sunburn/) tanning, skin aging and in severe sunburn cases, blistering. - **UVB** plays a key role in developing skin cancer. - **UVB** intensity fluctuates. While the sun’s rays are strongest and pose the highest risk late-morning to mid-afternoon from spring to fall in temperate climates and even greater timespans in tropical climates, UVB rays can damage your skin year-round, especially at high altitudes or on reflective surfaces like snow or ice. - **UVB** rays can be filtered and do not penetrate glass. ### UVA facts and risks - **UVA** rays cause skin damage that leads [tanning](http://skincancer.org/risk-factors/tanning/), as well as skin aging and wrinkles. The slightly longer UVA rays travel deeper into the skin layers to cause damage. The shorter wavelengths of UVA also contribute to sunburn. - **UVA** rays are proven to contribute to the development of skin cancer. - **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 or [tanning](https://skincancer.org/tanning). There is no such thing as a safe or healthy tan; a tan is a sign of sun damage. Over time, UVA also leads to premature aging and skin cancer. - **UVA** radiation is the main type of light used in most tanning beds. Once thought to be safe, we now know it is just the opposite. - **UVA is everywhere**. UVA accounts for up to 95 percent of the UV radiation reaching the earth. These rays maintain the same level of strength during daylight hours throughout the year. This means that during a lifetime, we are all exposed to a high level of UVA rays. - **UVA can penetrate** windows and cloud cover. ### What is the UV Index? The UV Index measures the intensity of [ultraviolet (UV) radiation](https://scfredesignsta.wpengine.com/risk-factors/uv-radiation/ "https://scfredesignsta.wpengine.com/risk-factors/uv-radiation/") from the sun at a location. It’s calculated using the latitude and altitude of that place, time of day, time of year, ground conditions, cloud cover and state of the ozone layer in the atmosphere. The UV Index is reported as a whole number between 0 and 11(+), with 0 indicating absolutely no sunlight (used only at night!) and 11 indicating extreme radiation, when you can burn in less than 10 minutes.   #### Daily Max UV Index New York, NY UV Index 2.2 (Low) Powered by ![AccuWeather Logo]() Check the UV Index in your city. **You Need Sun Protection Every Day.** The Daily Max UV Index is non-medical opinion and is for illustrative, discussion, and entertainment purposes only and should not be used for preventing, diagnosing, or treating a medical or health condition. ### Protect yourself! Despite the risk factors, you can safely, happily enjoy the great outdoors by [protecting your skin](http://skincancer.org/skin-cancer-prevention/sun-protection/) against UV exposure with [broad-spectrum sunscreen](http://skincancer.org/skin-cancer-prevention/sun-protection/sunscreen/) and sun-safe [clothing](http://skincancer.org/skin-cancer-prevention/sun-protection/clothing/), hats and [eyewear](http://skincancer.org/skin-cancer-prevention/sun-protection/eye-protection/). You can also consider [ UV window film](http://skincancer.org/blog/surprising-danger-planes-trains-automobiles/) for your home and car. **Make it a way of life.** Protect yourself every day, even when it’s cloudy. Avoid indoor tanning entirely. Get more details here: [Your Daily Sun Protection Guide](http://skincancer.org/skin-cancer-prevention/sun-protection/). ***Reviewed by: ****Anna Chien, MD* *Heidi Jacobe, MD* [Sunburn](http://www.skincancer.org/risk-factors/sunburn/ "Sunburn") [Skin Type](http://www.skincancer.org/risk-factors/skin-type/ "Skin Type") [Atypical Moles](http://www.skincancer.org/risk-factors/atypical-moles/ "Atypical Moles") [Tanning](http://www.skincancer.org/risk-factors/tanning/ "Tanning") [Photosensitivity](http://www.skincancer.org/risk-factors/photosensitivity/ "Photosensitivity") ## Sun & Skin News [Indoor Tanning 101: Do You Know the Risks?](https://www.skincancer.org/blog/indoor-tanning-101-do-you-know-the-risks/)![Caitlin Houston]() [Healthy Lifestyle](https://www.skincancer.org/blog/category/healthy-lifestyle/) [Tanning](https://www.skincancer.org/blog/category/tanning/) ### [Indoor Tanning 101: Do You Know the Risks?](https://www.skincancer.org/blog/indoor-tanning-101-do-you-know-the-risks/) [A Surprising Danger in Planes, Trains and Automobiles](https://www.skincancer.org/blog/surprising-danger-planes-trains-automobiles/)![holiday-travel]() [Healthy Lifestyle](https://www.skincancer.org/blog/category/healthy-lifestyle/) ### [A Surprising Danger in Planes, Trains and Automobiles](https://www.skincancer.org/blog/surprising-danger-planes-trains-automobiles/) [You Missed a Spot! Lower Your Skin Cancer Risk by Protecting These 6 Often-Missed Areas](https://www.skincancer.org/blog/you-missed-a-spot/)![sunburn-feet]() [Healthy Lifestyle](https://www.skincancer.org/blog/category/healthy-lifestyle/) [Skin of Color](https://www.skincancer.org/blog/category/skin-of-color/) ### [You Missed a Spot! Lower Your Skin Cancer Risk by Protecting These 6 Often-Missed Areas](https://www.skincancer.org/blog/you-missed-a-spot/) Last updated: July 2026 Open menu Menu Close menu SearchSearch ```json {"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.skincancer.org\/risk-factors\/uv-radiation\/","url":"https:\/\/www.skincancer.org\/risk-factors\/uv-radiation\/","name":"UV Radiation - The Skin Cancer Foundation","isPartOf":{"@id":"https:\/\/www.skincancer.org\/#website"},"primaryImageOfPage":{"@id":"https:\/\/www.skincancer.org\/risk-factors\/uv-radiation\/#primaryimage"},"image":{"@id":"https:\/\/www.skincancer.org\/risk-factors\/uv-radiation\/#primaryimage"},"thumbnailUrl":"https:\/\/www.skincancer.org\/wp-content\/uploads\/Beyond-the-sun.jpg","datePublished":"2019-07-02T18:19:48+00:00","dateModified":"2026-07-06T21:04:14+00:00","description":"Understand the basics about UV radiation and how it damages your skin, learn about the UV index and how to protect against skin cancer.","breadcrumb":{"@id":"https:\/\/www.skincancer.org\/risk-factors\/uv-radiation\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.skincancer.org\/risk-factors\/uv-radiation\/"]}]},{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.skincancer.org\/risk-factors\/uv-radiation\/#primaryimage","url":"https:\/\/www.skincancer.org\/wp-content\/uploads\/Beyond-the-sun.jpg","contentUrl":"https:\/\/www.skincancer.org\/wp-content\/uploads\/Beyond-the-sun.jpg","width":900,"height":376},{"@type":"BreadcrumbList","@id":"https:\/\/www.skincancer.org\/risk-factors\/uv-radiation\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.skincancer.org\/"},{"@type":"ListItem","position":2,"name":"Risk Factors","item":"https:\/\/www.skincancer.org\/risk-factors\/"},{"@type":"ListItem","position":3,"name":"UV Radiation"}]},{"@type":"WebSite","@id":"https:\/\/www.skincancer.org\/#website","url":"https:\/\/www.skincancer.org\/","name":"The Skin Cancer Foundation","description":"Education, prevention, early detection, and treatment of skin cancer","publisher":{"@id":"https:\/\/www.skincancer.org\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.skincancer.org\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.skincancer.org\/#organization","name":"The Skin Cancer Foundation","url":"https:\/\/www.skincancer.org\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.skincancer.org\/#\/schema\/logo\/image\/","url":"https:\/\/www.skincancer.org\/wp-content\/uploads\/SCF-Logo-2025-4C.png","contentUrl":"https:\/\/www.skincancer.org\/wp-content\/uploads\/SCF-Logo-2025-4C.png","width":1199,"height":1254,"caption":"The Skin Cancer Foundation"},"image":{"@id":"https:\/\/www.skincancer.org\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/www.facebook.com\/skincancerfoundation","https:\/\/x.com\/skincancerorg","https:\/\/www.instagram.com\/skincancerorg\/","https:\/\/www.linkedin.com\/company\/the-skin-cancer-foundation\/","https:\/\/www.pinterest.com\/skincancer\/","https:\/\/www.youtube.com\/user\/SkinCancerFoundation","https:\/\/en.wikipedia.org\/wiki\/Skin_Cancer_Foundation","https:\/\/www.tiktok.com\/@skincancerorg"],"description":"The Skin Cancer Foundation saves and improves lives. We empower people to take a proactive approach to daily sun protection and the early detection and treatment of skin cancer.","email":"info@skincancer.org","telephone":"(212) 725-5176","legalName":"The Skin Cancer Foundation"}]} { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "What is UV radiation?", "acceptedAnswer": { "@type": "Answer", "text": "UV radiation is part of the natural energy produced by the sun. On the electromagnetic spectrum, UV light has shorter wavelengths than visible light — your eyes cannot see UV, but your skin can feel it. Tanning beds also emit UV radiation. UV radiation is a proven human carcinogen. Two types of UV light are proven to contribute to the risk of skin cancer: UVA, which has a longer wavelength and is mainly associated with tanning, skin aging, and skin cancer; and UVB, which has a shorter wavelength and is mainly associated with sunburn. Both UVA and UVB rays damage the DNA in skin cells, producing genetic mutations that can lead to skin cancer and premature aging." } }, { "@type": "Question", "name": "Does UV radiation cause skin cancer?", "acceptedAnswer": { "@type": "Answer", "text": "Yes. UV radiation is a proven human carcinogen and the primary cause of most skin cancers. The majority of nonmelanoma skin cancers and a large percentage of melanomas are associated with UV radiation exposure from the sun. Unprotected exposure to UVA and UVB rays damages the DNA in skin cells, triggering mutations that cause cells to multiply rapidly and can lead to malignant tumors. Research shows that UV rays can also alter a tumor-suppressing gene, raising the risk that sun-damaged skin cells will develop into cancer. UV damage is cumulative — it builds up over time, and the body cannot repair all of it." } }, { "@type": "Question", "name": "What is the difference between UVA and UVB rays?", "acceptedAnswer": { "@type": "Answer", "text": "UVA and UVB are two types of ultraviolet radiation that affect the skin differently. UVA has a longer wavelength, penetrates the skin more deeply into the innermost part of the top layer (where most skin cancers occur), and is mainly associated with tanning, premature skin aging, and skin cancer. UVA accounts for up to 95 percent of UV radiation reaching the earth and maintains the same level of strength during daylight hours throughout the year. UVA can penetrate windows and cloud cover. UVB has a shorter wavelength, penetrates the outermost layers of skin, and is mainly associated with sunburn. UVB intensity fluctuates by season, time of day, and altitude, and is strongest from late morning to mid-afternoon in spring through fall. UVB rays can be filtered and do not penetrate glass. Both types cause DNA damage and increase skin cancer risk." } }, { "@type": "Question", "name": "What does UVA radiation do to skin?", "acceptedAnswer": { "@type": "Answer", "text": "UVA rays penetrate deeply into the skin, reaching the innermost part of the top layer where most skin cancers occur. UVA causes tanning (the skin's attempt to prevent further damage by darkening), premature skin aging including wrinkles and age spots, and contributes to the development of skin cancer. UVA radiation is the main type of light used in most tanning beds, and despite early assumptions that it was safe, it is now known to be just as dangerous as UVB. UVA accounts for up to 95 percent of the UV radiation reaching the earth's surface and remains at consistent levels throughout the day and year — it can penetrate windows and cloud cover, meaning indoor and overcast-day exposure still carries risk." } }, { "@type": "Question", "name": "What does UVB radiation do to skin?", "acceptedAnswer": { "@type": "Answer", "text": "UVB rays penetrate and damage the outermost layers of the skin. Overexposure causes suntan, sunburn, and in severe cases, blistering. UVB is connected to the Sun Protection Factor (SPF) rating on sunscreen products — the SPF number indicates how long the sun's radiation would take to redden your skin using that product compared to without it. UVB intensity fluctuates by season, time of day, and geography: the rays are strongest and highest-risk from late morning to mid-afternoon, spring through fall, in temperate climates, and even longer periods in tropical climates. UVB risk is also elevated at high altitudes and on reflective surfaces like snow or ice. Unlike UVA, UVB rays can be filtered and do not penetrate glass." } }, { "@type": "Question", "name": "Can UV rays come through windows?", "acceptedAnswer": { "@type": "Answer", "text": "UVA rays can penetrate standard window glass and cloud cover, meaning you can receive significant UV exposure while indoors near a window, in a car, or on an overcast day. UVB rays, by contrast, are filtered by glass and do not penetrate it. Because UVA maintains consistent strength throughout the day and year regardless of weather, the cumulative UV damage from sitting near windows, driving, or working in naturally lit spaces adds up over time. UV-protective window film for homes and vehicles can help reduce this ongoing UVA exposure." } }, { "@type": "Question", "name": "What is the UV index and how does it work?", "acceptedAnswer": { "@type": "Answer", "text": "The UV index measures the intensity of ultraviolet (UV) radiation from the sun at a specific location. It is calculated using the latitude and altitude of the location, time of day, time of year, ground conditions, cloud cover, and the state of the ozone layer in the atmosphere. The UV index is reported as a whole number between 0 and 11+, with 0 indicating no sunlight (used only at night) and 11+ indicating extreme radiation, at which unprotected skin can burn in less than 10 minutes. A higher UV index means unprotected skin will burn faster or more severely. However, even when the UV index is low, UV radiation is still present and sun protection remains necessary every day of the year." } }, { "@type": "Question", "name": "What does 'broad-spectrum' sunscreen protection mean?", "acceptedAnswer": { "@type": "Answer", "text": "Broad-spectrum protection means that a sunscreen protects against both UVA and UVB rays. Early sunscreens only protected against UVB rays, which cause visible sunburn. Once the dangers of UVA rays — deeper skin penetration, premature aging, and skin cancer — became better understood, sunscreen manufacturers began adding ingredients to protect against the full spectrum of UV radiation. A sunscreen labeled broad-spectrum provides protection from both types of UV radiation. The Skin Cancer Foundation recommends using a broad-spectrum sunscreen with SPF 30 or higher every day." } }, { "@type": "Question", "name": "How can I protect myself from UV radiation?", "acceptedAnswer": { "@type": "Answer", "text": "You can greatly reduce the danger posed by UV radiation by taking consistent protective measures: apply a broad-spectrum sunscreen with SPF 30 or higher every day, reapplying every two hours and after swimming or sweating; wear sun-protective clothing, a wide-brimmed hat, and UV-blocking sunglasses; seek shade especially during peak UV hours (10 AM to 4 PM); avoid indoor tanning entirely; consider UV-protective window film for your home and car to reduce UVA exposure indoors; and check the daily UV index to understand your exposure level. Sun protection should be practiced every day, year-round, even when it is cloudy — UV rays can still damage your skin through cloud cover." } } ] } ```