Our Community Blog Sunscreen explained by a dermatologist June 2020 Sunscreens can be confusing! You will often see numbers, star ratings, words like ‘mineral’ and ‘zinc oxide’, ‘organic’ and ‘natural’. What do all these mean and what is the best sunscreen for you? I’ll try to demystify the jargon and address some common misconceptions regarding sunscreens. Why use sunscreen at all? In 2017 there were approximately 14,000 new cases of melanoma and 147,000 cases of non-melanoma skin cancers. Melanoma and certain non–melanoma skin cancer can be fatal. The cases of melanoma have dramatically increased over the years. The sun emits ultraviolet radiation in the form of UVA and UVB (also UVC which does not reach the earth surface). Years of research has confirmed that both these rays can cause melanoma and non- melanoma skin cancers. Sunscreen successfully prevents most of these rays from reaching our skin and thus reducing our risk of skin cancer. Melanoma skin cancer What is the difference between UVA and UVB? The sun emits three types of radiation UVA and UVB and UVC. UVA: Accounts for 95% of the radiation that reaches the earth’s surface. This type of radiation can penetrate the skin deeper than UVB and due to its longer wavelength can pass through clouds and glass. It has skin cancer causing potential and also results in premature skin ageing and pigmentation. UVB: These rays cause skin burning and reddening. They do not penetrate the skin as deeply however the majority of skin cancers are due to UVB. UVC: This has the shortest wavelength and is the most damaging type, however it is completely filtered by the atmosphere and therefore does not reach the earth surface. Any easy way to remember is UVA= Ageing and UVB = Burning. However both can cause cancers. What does the SPF number mean? All sunscreens will display a number that is followed or preceded by the letters SPF (sun protection factor). Remember the SPF only refers to the sunscreens potential to block UVB rays and not UVA. SPF numbers range from 2 to 50+. The numbers tell you the time the skin will take to redden with the sunscreen versus the amount of time it will take to redden without the sunscreen. So if you have appropriately applied an SPF 15, it would take your skin 15 times longer to go red as compared to having no sunscreen on. So if your skin normally reddens after 10 mins in the sun, applying an SPF 15 sunscreen would allow you stay in the sun for 150 mins. The higher the number the longer the protection. However SPF is actually a measure of the degree of protection it gives you from UVB rays and should not be used to determine the length of sun exposure. An SPF of 30 allows about 3% of UVB to penetrate the skin and SPF 50 about 2%. This does not seem much but can make a big difference in certain skin types. How do I protect against UVA radiation? Image courtesy of Walgreen Boots Alliance The UVA seal – a logo with ‘UVA’ inside a circle indicates that the product conforms to EU recommendations for UVA protection which is equivalent to at least one third of the SPF. Often you will see a star rating for UVA, ideally pick one with a minimum of 4 stars. In the USA and Japan a scale of PA values is used to denote UVA protection. PA + (Low) to PA ++++ (High). What is the difference between a physical, organic and chemical sunscreen? What do the ingredients mean? There are two main types of sunscreen available on the market. Chemical sunscreens: They are also known as organic sunscreens or synthetic sunscreens. These are the most commonly used sunscreen and work by absorbing the UV light and releasing as heat. The following chemicals (amongst others) will denote a chemical sunscreen: Oxybenzone Avobenzone Octisalate Octocrylene Homosalate Octinoxate Chemical sunscreen absorbs into the skin and as a result can sometimes result in irritation. Ideally they need to be applied 20 mins before sun exposure. They tend to have a thinner texture, spread more easily on the skin and are preferred by most consumers. However due to the chemical composition these types of sunscreens will be ‘used’ up quickly when in direct sun and as a result will need to be applied regularly. Mineral sunscreen: Also known as physical sunscreens, these work by absorbing and then scattering or deflecting the UV radiation. There two chemicals used: Titanium dioxide Zinc Oxide Mineral sunscreens provide protection from the sun immediately after application. They tend to last longer in the sun; however will be washed off with sweat and water. They are less irritant on the skin. They leave whitish cast on the skin and therefore are often not cosmetically acceptable for people with darker skin tones. Often larger amounts are required to achieve adequate protection. Which sunscreen should I use? The best sunscreen is the one you will use regularly and in the correct quantities. The type of sunscreen will be dependent on the type of outdoor activity you’ll be engaged in or your skin type. There are a variety of sunscreen types you can choose from: Water resistant: These are good for use during water activities, they will need to be reapplied, however no sunscreen is truly waterproof. Spray sunscreen: Sprays are used mostly for their convenience however these should be sprayed onto the skin until it appears wet and then rubbed in with your hands – so actually, if used correctly, it may not be as convenient as you would imagine. They should also not be sprayed directly on the face or the head. There are some concerns with regards to children breathing in the spray particles however more research is needed into whether this is harmful or not. Sensitive skin: A mineral or physical sunblock is less irritant and suitable for those with sensitive or acne prone skin. Natural sunscreens: Sunscreens labelled as natural tend to be mineral based therefore containing zinc or titanium. They are good for immediate protection. Broad Spectrum: This means that there is protection against both UVA and UVB. Therefore this should be part of any sunscreen you apply. How much should I apply? The advice is for all sunscreens to be applied two hourly and more often if you sweat or have been in water. Some sunscreens suggest that they may be a once daily application; I do not recommend a single application of any sunblock for the whole day. About 67% of British people do not use enough sunscreen. Overall for adults an amount that is equivalent to a full shot glass is adequate. Face and neck: Half a teaspoon Arms: One teaspoon Legs: Two teaspoons Front and Back of torso: Two teaspoons What is the correct SPF for me? If you plan on spending longer than 15-20 mins in the sun then I would recommend a minimum of SPF 30. However if you are very fair, with blue eyes and blonde, that is to say you have Type 1 skin, an SPF 50 will be required. You can determine your skin type by looking at the Fitzpatrick Skin Type chart. Babies under the age of 6 months should not be in direct sunlight and older children should be applying SPF 50. Image courtesy of the British Association of Dermatologists Will I become deficient in Vitamin D if I use too much sunscreen? There is no evidence to suggest this. A recent study showed that even with regular and appropriate application of sunscreen there was excellent synthesis of Vitamin D. Hopefully this should answers some questions with regards to sunscreen use. Please make sure in addition to avoid the midday sun, wear a broad-brimmed hat and protect your eyes with sunglasses that have 100% UV protection. Dr Adil Sheraz, Consultant Dermatologist Find Dr Sheraz on Twitter and Instagram. Donate to skin cancer research More on sunlight and vitamin D By donating to skin disease research you are helping us to find treatments and cures for common conditions like eczema, acne and psoriasis through to potential killers like melanoma skin cancer. Thank you.