From best-before dates to how much to use, the UVA to Z of staying sun-safe and picking the right tanning lotion

THE sun has finally arrived but finding the right stuff to protect our bodies from the rays is a minefield.

Dermatologist Dr Anjali Mahto of the British Skin Foundation gives LAURA STOTT expert advice.

What is the difference between SPF numbers?

SPF — Sun Protection Factor — measures how well a sunscreen blocks out UVB radiation from the sun.

UVB rays cause burning and are linked to skin cancers, so the higher the SPF the greater the protection.

Guidelines recommend a minimum SPF 30 for most of us. But anyone at high risk of cancer or other skin conditions should opt for SPF 50.

Remember that any tan indicates that the skin has been damaged by UV rays. The only way to tan safely is from a bottle.

What is the difference between UVB and UVA?

These are the two forms of ultraviolet radiation from the sun and both can cause damage that may lead to skin cancers. UVA rays are long.

They penetrate into the deeper layers of the skin and cause long-term ageing effects such as lines, wrinkles and brown pigmentation marks known as sun spots. UVA can still penetrate your skin through windows and clouds.

UVB rays are shorter and cause surface damage such as sunburn, which can then lead to skin cancers like melanomas. An easy way to remember the difference is to think A is for ageing and B is for burning.

Always ensure you look for a four or five-star UVA rating on your sunscreen bottle to protect from radiation effects associated with skin ageing. A high SPF rating will help prevent sunburn and damage caused by UVB rays.

Should I still wear SPF if I am in the shade?

Seeking shade gives shelter from heat and glare but you still need to slather on protection.

Damaging UV rays can still reach skin indirectly by bouncing from sunnier spots.

This means you remain exposed to the harm they can cause. Wear sunscreen in the shade in conjunction with other sun safety measures such as covering up,

Especially between 11am-3pm when the UV index is highest.

How much sunscreen do you need to use?

Probably more than you think. An average-sized adult should apply more than half a teaspoon of sunscreen to each arm and the face and neck areas.

You need just over one teaspoon for each leg, the front and the back of the body. Be generous and apply everywhere — not forgetting areas like ears, the scalp and neck.

How long before going outside should you apply suncream? Apply 15 to 30 minutes before going outside to allow it to dry properly. Once in the sun keep your eyes peeled for any patches you may have missed which require attention.

Reapply a minimum of every two hours and always top up straight after swimming, sweating or towel-drying, even with a one-a- day formula.

Does price make any difference to protection?

No. The key thing to look for is SPF 30 or more to shield against UVB and four or five UVA stars for protection against other skin-ageing rays.

Expensive sunscreens are not necessarily best and cheaper ones are not necessarily worst. Think protection, not price.

Does water-resistant mean you’re protected when swimming?

Water-resistant sunscreen will only withstand around two short swims in the pool or sea.

It is not completely waterproof. Sunscreen will also be rubbed off when towel drying. It is always safest to reapply after a dip.

What should I use for babies and children?

Always use a sunscreen with a minimum of SPF 50 with maximum UVA stars.

Fragrance-free or hypoallergenic creams generally work best as they contain fewer allergens which could potentially irritate. Always keep babies and young children out of direct sunlight.

Does suncream go off?

Yes — all of them will display a best before date. There is also a Period After Opening (POA) date on the back.

This is a number — such as 12M for 12 months — displayed in the middle of a ­symbol that looks like an open jar. If it has been open longer than the months shown then you need to replace it.

What formula should I choose?

There are two main types of sunscreen: Chemical and physical. Chemical sunscreens reduce the level of UV penetrating the skin.

Physical or mineral sunscreens physically block them. If you have sensitive skin then physical sunscreens may be less irritating, but they can be chalky in consistency and thicker to apply. A gel, oil, spray or cream formula is often personal preference.

Does make-up with SPF still protect me in the sun?

Cosmetics containing SPF are usually not applied thickly enough to get a safe level of ­protection. Also, if applied in the morning, they will lose effectiveness or rub off by the middle of the day when the UV index is highest.

Always use a separate high-factor sunscreen for your face and do not rely on the SPF in your make-up to do the job.

How best should you treat sunburn?

If your skin has started to burn get out of the sun quickly and reduce heat and swelling with a cool — but not ice-cold — shower, bath or cloth compress.

Aim to have the temperature just below lukewarm. Pat dry, do not rub, then apply a fragrance-free lotion or cream to help soothe and prevent peeling.

Aloe vera gel can also work well applied topically, acting as a cooling anti-inflammatory. Continue to apply for several days as skin heals.

Taking Ibuprofen tablets can offer relief if skin is sore and will also help to reduce inflammation. Paracetamol will help if you are in pain but will not reduce inflammation. As your skin heals, do not scratch or pick at peeling skin or blisters. ­

Cover up with loose, breathable fabrics such as cotton and stay in the shade — do not expose burnt areas to direct sunlight again until the skin has healed fully.

If skin is blistered or swollen, or you feel dizzy, sick or have a high temperature seek medical advice as you may have heat stroke.