The industry guideline for water-resistant sun creams allows the SPF of a product to drop by 50% after a total of 40 minutes in water. Water-resistance testing also takes place in what is essentially a bath – using tap water. Cover up – wear sunglasses to protect your eyes and grab a hat if you need to keep your face out of the sun. You might also want to wear a T-shirt, which can help to cover up typically over-exposed areas such as shoulders. Consider the time of day – If you're spending time in the sun without wearing sun cream, you should only do so before 11am or after 3pm, as the middle of the day is when you're at the greatest risk of getting burnt. Eat well, live better and stay healthy - sign up for our free monthly Food & Health newsletter for the latest insights delivered straight to your inbox Important: Read the instructions carefully before use. Apply to clean dry skin, preferably after a shower. Apply evenly and generously 15 minutes before exposure to the sun, which will allow the product to bind with the skin and form a protective film against UVA/UVB rays. When used correctly, one application is sufficient for all day protection.

For reasons of hygiene and safety, personal grooming products, cosmetics or items of intimate clothing cannot be returned. Babies less than six months old should be kept out of direct sunlight, according to the NHS, and the skin of young children should be protected from the sun when UV levels are high. When choosing sun cream for your child, look for a short ingredients list and the terms 'fragrance free' and 'hypoallergenic'. The WHO recommends 35ml of sun cream (seven teaspoons' worth) to cover an adult, so use around a quarter to a half of this depending on the size of your child. We tested two popular sun creams in chlorinated water (to mimic a swimming pool) and salty water (to emulate the sea). We also added another scenario using fast-moving tap water to see what effect this had. Most of the time, the products weren't as effective in our more realistic conditions as they were in tap water.

Apply evenly and generously, smooth in gently. We recommend a minimum quantity of 35ml for all over body protection.

Remember, sun cream is just one part of staying safe in the sun and it's also really important to encourage kids (and adults) to: Some people worry that using sun cream might prevent them from getting enough vitamin D, but this isn’t the case unless you really overdo it. Find out what you need to know about 'once a day' sun creams, water-resistant sun creams, sensitive sun screen and the best kids' sun cream too. Mineral sunscreens in particular often promote their environmental credentials, the most common being that they’re ‘reef-safe’ or 'ocean-friendly'.

Physical or mineral sun creams create a barrier on the skin that acts like a mirror, reflecting and scattering the UV light. Do not exceed exposure to the sun for longer than your skin type allows, taking into account the strength of the sun.

If you're using sun cream at the beach, apply plenty before swimming, and again when you leave the water. Reef-safe sun creams We award Which? Best Buy status to products that we've independently reviewed that meet all our tough criteria: they must pass independent lab tests for UVA and UVB sun protection, and be easy and pleasant to apply. However, there's no agreed definition of 'reef-safe', research is still ongoing as to the impact of these chemicals, and our tests found many mineral suncreams failed to protect as claimed – so take any claims with a pinch of salt. Kids' sun cream Sun cream provides protection from sunlight using UV filters. These are classified into two types: chemical and physical – also known as mineral sun cream. This tends to mean that two commonly used chemical UV filters linked to coral bleaching – oxybenzone and octinoxate – aren’t used.Avoid sun exposure between 11am - 3pm. Seek shade and always protect children with a hat, loose clothing and high SPF protection. It takes longer for those with darker skin that rarely burns – it can take 25-40 minutes for the darkest skin type.