With a heatwave reportedly due to hit the UK next week, it’s important to keep in mind the risks posed by overexposure to the sun; namely sunburn.

In this post, we’ll discuss with Treated.com Clinical Lead Dr Daniel Atkinson the various different stages of sunburn, when they are most likely to occur, and how to ensure you stay protected.


(15 minutes or more)

How long it takes to sustain sunburn depends on a number of factors, such as how warm it is, the time of day, and how light (or susceptible to UV rays) your skin is.’ Dr Atkinson explains.

But on particularly hot days, people with fairer skin may only need to be out in the sun for as little as 15 minutes to develop signs of sunburn later on. Obviously the longer you stay exposed, the more likely you are to get sunburn, and you may experience more severe levels of sunburn.

It usually doesn’t become visibly apparent to someone that they have been burnt until an hour or two later. It’s therefore very easy, during the exposure period, not to notice that you’re getting burnt.

What causes sunburn?

UV rays, which cause sunburn, tend to reach their peak between the hours of 11am and 3pm; this is when the sun is at its highest point in the sky. So for people who are susceptible to sunburn, this part of the day is the higher risk window.’


(from 2 hours onwards)

Exposure to UV rays inflicts damage on skin cells, which sparks an inflammatory response in the body.’ Dr Atkinson tells us. ‘This is where the immune system perceives something as a threat, so releases chemical transmitters to ‘tell’ us that a part of the body is injured; in this case the skin. This comes in the form of redness (and later, pain).’

In more severe cases and in people who are particularly sensitive to sunburn, the affected area of skin may become pink and then red inside an hour; but in most cases, it will take two hours or more for signs of sunburn to show.’

Someone with mild sunburn is likely to be red for the next few days after exposure, although it may gradually fade during this time. Moderate sunburn and more severe cases may take longer (several weeks) to completely fade.’


(from 6 hours onwards)

‘The next stage is pain and soreness in the affected areas.’ Dr Atkinson explains. ‘Again, how severe this is and how long it lasts for depends on the extent of the burn. In most cases, someone will notice pain the most from around six hours onwards following exposure.’

Sunburnt skin is also much more sensitive to heat; so if someone who has sunburn goes back out into the sun or takes a warm or hot shower, they’ll experience more discomfort.’

People who are badly burnt may also develop blisters. This type of sunburn is a sign of the body trying to protect itself from further damage and expedite healing; blisters function as a barrier between healing tissues and the surface of skin.’


(from 2 days onwards)

When the worst of the pain has subsided, peeling may occur; usually after a couple of days. This can last for up to a week, again depending on how bad the burn is or how large an area it covers. Someone with only mild sunburn may only peel for a day or two.’ Dr Atkinson tells us.

In the sunburn stages, peeling is a sign of the body getting rid of damaged skin cells in order to replace them with new, healthy ones.’

Preventing sunburn

We need some sun exposure in order to maintain a healthy supply of vitamin D. But getting burnt through overexposure also increases the risk of various types of skin cancer, and can contribute to premature aging and skin conditions like actinic keratosis.

So while some sunlight is good for us, taking precautions is absolutely crucial, as Dr Atkinson explains:

  • 'Make sure you apply sunscreen to exposed areas of skin, ideally around half an hour before going out, and re-apply according to the instructions every couple of hours while you’re out. A lot of people tend not to put enough sunscreen on; too thin a layer doesn’t sufficiently reduce the risk of sunburn. As a rough guide, an adult should use about 35ml per application. SPF 15 might not be enough for people with fairer skin. If you’re sensitive to the sun, it’s worth thinking about using SPF 30. You should also ensure the product you’re using offers both UVA and UVB protection.
  • On very warm days, considering wearing loose, light clothing with long sleeves and trouser legs to cover your arms and legs, and protect them from UV rays. A hat with a wide brim also helps to limit the risk of getting a burnt neck. Wearing sunglasses can also limit the risk to skin on your face and around the eyes.
  • Peak hours for UV intensity are between 11am and 3pm, so it can be useful to limit exposure during these hours. If the shadow you cast is shorter than your actual height, it means the sun is high in the sky and therefore particularly strong.
  • If you’re going to be outside for long periods in hot conditions, try to stay in the shade as much as possible.'

Caring for sunburn

If it’s too late and you’ve already sustained sunburn, Dr Atkinson explains that there are measures you can take to reduce discomfort and help you through your sunburn healing time.

  • ‘Apply an after sun cream or aloe vera moisturiser to soothe skin irritation.’
  • ‘Have a cold shower to help cool the skin down.’
  • ‘Drink plenty of fluids to help the body stay cool and hydrated.’
  • ‘Over the counter painkillers can help to ease pain and soreness.’

‘If you have particularly bad sunburn or become otherwise unwell, speak to your GP. This might be if you have blisters, feel dizzy or have a fever, or if your sunburn has occurred over a large surface area.’