How often should you apply sunscreen in heatwave? When to reapply in hot weather - and NHS advice explained

The UK is currently sweltering in one of its hottest heatwaves on record, with temperatures soaring into the late 30s across much of England and Wales.

The extreme hot weather poses a major risk to health, with the Met Office and UK Health Security Agency (UKHSA) issuing the highest level of heat health alert for an area stretching from London to Manchester.

While people are being urged to avoid the sun, many people have flocked to the nation’s beaches and parks.

But if you’re intending to do a spot of sunbathing, how much sunscreen do you need to have on - and how often do you need to reapply it?

Here’s everything you need to know.

What strength sunscreen do you need?

The NHS recommends staying out of the sun in the UK between the hours of 11am and 3pm between March and October.

But if you’re out and about or want to catch some rays, it says you ought to wear sunscreen to avoid burning.

It gives this advice because sunburn can increase your risk of developing skin cancer.

The weather does not necessarily have to be hot to burn you.

When applying sunscreen, there are two key things you need to think about:

1. How strong the sunscreen is
2. How much of it you’re applying

Sun cream strength is measured using a scale known as SPF - or ‘sun protection factor’.

You’ll see this figure noted on any bottle of sunscreen or fortified moisturiser you purchase.

It denotes how much protection you will get from UVB rays - a spectrum of ultraviolet light that can be harmful to humans.

The NHS recommends using a minimum of SPF 30.

If applied correctly, this level of protection should essentially provide an extra 30 layers of strength to your skin.

So, say you typically start to burn after spending 15 minutes in the sun, wearing this level of SPF will in theory give you 30-times as long before you begin to burn - around 7.5 hours, although it will most likely only last for two to three hours.

You can purchase sun creams on the high street that provide an SPF of up to 100 - although factor 50 is the highest strength you will most commonly see.

The NHS also suggests purchasing a sunblock that has four-star UVA protection - UVA being another spectrum of ultraviolet light which can also be harmful.

How often should you reapply sunscreen?

To begin with, you should apply sunscreen properly.

The NHS says you can do this by slapping on two teaspoons (almost 12ml) of sunblock if you are only covering your head, neck and arms.

If you need to cover almost your entire body, you should squeeze out the equivalent of two tablespoons (just under 30ml).

To ensure you are getting a good coating all over your unprotected areas, it might be worth asking a loved one to put it on for you in hard to reach places, like your back.

While the health service does not give a time limit for how often you should reapply sunscreen, it urges people to put it on “liberally and frequently” and to check the manufacturer’s instructions on the bottle.

One potential time limit you could use is two hours, as that’s how long the NHS says it takes for the sun to dry suncream off your skin.

If you have been for a swim, or have been sweating, it recommends that you reapply your sun cream as soon as possible.