No matter where you live, protecting your skin from the sun matters. One of the best tools for the job is sunscreen, which shields your skin from harmful radiation. Daily sunscreen does more than save you from sun damage, since it also lowers your chances of developing skin cancer. In this article we look at the science behind sunburn and skin damage, how SPF works and the different types of sunscreen. The aim is to help you protect yourself from the rays you meet every day.
What is the Science of Sunburn & Skin Damage?
Sunburn is a common and painful condition that happens when the skin meets the sun’s harmful UV rays for an extended period without proper protection. It can have both immediate and long-term effects on the skin. UV rays, particularly UVB, penetrate the skin’s outer layer and damage the DNA in skin cells. When that DNA is damaged, it triggers a protective response. The blood vessels in the skin dilate, which causes the redness and inflammation we associate with sunburn. The damaged cells also release chemicals that stimulate nerve endings to produce pain and discomfort.
In response, the skin may peel and become dry and itchy as it sheds damaged cells and tries to repair itself. Over time, repeated sun exposure and sunburn lead to longer-term effects. Sun damage can cause premature ageing of the skin. It can also raise the risk of skin cancer, including common types such as basal cell carcinoma, squamous cell carcinoma and melanoma. UV radiation is the leading cause of skin cancer, and most skin cancers relate directly to sun exposure. This is why sunscreen is so important for preventing the kind of skin damage that may lead to cancer.
What Does SPF Mean & How Does it Work?
Sunscreen uses active ingredients that absorb or scatter UV rays before they penetrate the skin, which reduces how much radiation reaches it. Two types of UV ray damage the skin, UVA and UVB. UVA rays prematurely age the skin and are linked to skin cancer, whilst UVB rays are the leading cause of sunburn. SPF stands for sun protection factor, and it measures how well a sunscreen protects the skin from UVB radiation, the main cause of sunburn.
Sunscreen products show SPF as a number, such as SPF 15, SPF 30 or SPF 50, representing the amount of protection on offer. The SPF number also indicates how much longer you can stay in the sun without burning compared with wearing no sunscreen at all. For example, if you would normally burn after 10 minutes, an SPF 15 product would in theory let you stay out for around 150 minutes (10 minutes multiplied by 15). This only holds if you apply and reapply it correctly. The active ingredients, whether organic or inorganic, act as a barrier that absorbs or reflects UVB rays. This helps prevent sunburn and reduce the risk of skin cancer.
It is essential to remember that SPF only measures protection against UVB rays. It does not necessarily reflect protection against UVA rays, which also contribute to skin damage and skin cancer. This is why you should choose a broad-spectrum sunscreen that protects against both. Higher SPF values give more defence against UVB rays, but the increase is not proportional to the number. For example, SPF 30 filters out about 97% of UVB rays, whilst SPF 50 filters about 98%. As a general rule, a minimum of SPF 30 is sensible. Even so, you should also stay in the shade and wear protective clothing and hats, since no sunscreen blocks 100% of UV radiation.
What’s the Difference Between Chemical & Physical Sunscreen?
There are two main types of sunscreen, chemical and physical. They protect the skin in different ways, which affects how they feel and who they suit best.
Chemical sunscreens contain organic (carbon-based) compounds as their active ingredients. These absorb UV radiation before it penetrates the skin, usually using a combination of compounds. Once applied, they form a protective layer that absorbs UV rays and converts them into heat, which the skin then releases.
Physical or mineral sunscreens contain inorganic compounds, usually zinc oxide or titanium dioxide. They sit on top of the skin and form a barrier that reflects and scatters UV rays away. Physical sunscreens do not absorb into the skin and protect immediately on application.
The choice between them comes down to your personal preferences and needs, including your skin type, sensitivity and activity level. Chemical sunscreens tend to be lightweight and easy to apply, with a thinner consistency that suits everyday use and layering under makeup. They often offer broad coverage against both UVA and UVB too. However, some people with sensitive skin react to certain chemical filters with irritation or allergy. Physical sunscreens tend to be thicker and may leave a white cast because of their reflective ingredients, but those with sensitive skin generally tolerate them better. Their immediate protection also makes them a good option for sensitive skin, babies and children.
What are Broad-Spectrum & Water-Resistant Sunscreens?
Broad-spectrum sunscreen protects the skin from both UVA and UVB rays. Choosing one is therefore important for safeguarding against the harmful effects of each. Water-resistant sunscreen is formulated to hold its effectiveness when exposed to water, sweat or moisture. It keeps protecting for a set period even when your skin is wet. It is worth remembering that water-resistant does not mean waterproof, so you still need to reapply after swimming, sweating or towelling off.
When choosing a sunscreen that offers both broad-spectrum and water-resistant protection, a few factors help.
- Look for the term broad spectrum on the label.
- Check the SPF rating, since SPF 30 or higher is recommended for adequate protection.
- For water resistance, look for the stated duration, such as 40 or 80 minutes.
- Consider the formulation, since thicker formats like lotions or sticks often hold up better in water.
- Match the product to your activity level and how much water or sweat you expect.
How Do You Apply Sunscreen Effectively?
Applying sunscreen correctly is essential to getting the full benefit. A few tips help you get it right.
- Use enough to cover all exposed skin. As a rule, that is half to one teaspoon for the face and neck and 6 to 8 teaspoons for an adult body.
- Spread it generously and evenly across the face, neck, ears, arms, legs and any other exposed areas.
- Pay attention to commonly missed spots like the back of the neck, the tops of the ears and the backs of the hands.
- Reapply every two hours, or straight after swimming, sweating or towelling off, as well as after heavy rubbing.
- Avoid common mistakes like using too little, skipping reapplication after sweating or swimming, and missing exposed areas.
- Choose a broad-spectrum sunscreen with SPF 30 or higher for the best protection against UVA and UVB.
When Should You Reapply Sunscreen?
As a rule, reapply every two hours or immediately after swimming, sweating or towelling off. A few other factors change how often you need to top up, though. If you spend long stretches outdoors, especially during peak hours (typically 10am to 4pm), you may need to reapply more often. The sun’s intensity shifts through the day. Vigorous exercise can rub or wash sunscreen away, which reduces protection and calls for more frequent reapplication. Some formulas also wear off faster than others, so choose a good-quality product and follow the manufacturer’s reapplication advice.
To reapply effectively through the day, these habits help.
- Carry a travel-sized bottle so topping up is easy.
- Cover all exposed skin, paying attention to commonly missed areas.
- Use the same amount as your first application and spread it generously and evenly.
- Avoid wiping sunscreen off when towelling, and reapply straight after swimming or sweating.
- Reapply to areas that clothing covers too, since fabric does not always block UV well.
Reapplying diligently keeps your skin protected from the sun’s UV radiation through the day.
What are the Other Forms of Sun Protection?
Sunscreen alone is not always enough to safeguard your skin from UV radiation. A few other measures add valuable protection. Clothing and accessories offer an extra protective layer. Opt for tightly woven fabrics that provide more coverage and a higher UV rating, and remember that darker colours absorb more UV than lighter ones. Wide-brimmed hats shade the face, neck and ears, whilst sunglasses protect your eyes from UV rays.
Seeking shade is another effective approach. When the sun is at its peak, stay in the shade as much as you can. Where none exists, use an umbrella, beach tent or other portable shade. Sun protection matters in many settings, not just at the beach or pool. UV radiation can still reach you in shaded areas, on cloudy days or during activities like hiking, gardening or sport. It is worth prioritising protection whatever the setting or weather, by combining sunscreen, protective clothing and shade to minimise your skin’s exposure.
Looking after your skin and protecting it from UV rays is essential. Sun damage does more than cause sunburn, since melanoma affects over 16,700 people in the UK each year, and proper UV protection helps prevent it. Remember that sun protection is a year-round effort.
At City Skin Clinic, we are passionate about personalised skincare. We offer custom skin and hair loss treatments using prescription-strength ingredients including tretinoin and hydroquinone where appropriate. Our doctors treat conditions including acne, hyperpigmentation, melasma and skin ageing via bespoke compounded treatments designed around you. Book a video consultation or start your online consultation today. Your journey towards great skin starts here.
This article is intended for general informational purposes only and is not a substitute for medical advice, diagnosis or treatment. Always consult a qualified medical professional with any concerns about your skin or treatment options.
