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What is sunburn?
Sunburn is damage caused to the skin when it is exposed to an excessive amount of ultraviolet (UV) light, a form of radiation that is part of sunlight.
UV light can penetrate and affect the skin. It is commonly found in sunlight, but is also the light used in tanning beds/solariums. Unlike light in the visible spectrum (which you can see) and light in the infra-red spectrum (which you can feel as heat), it is not possible to sense UV light. For that reason, when you're out in the sun, it can be difficult to know how much exposure to UV light you've had.
There tends to be more UV during the middle of the day and during summer, but sunburn can happen in cool, cloudy conditions as well. In some conditions, sunburn can occur within 15 minutes.
Skin is made up of three layers:
- Epidermis - the outermost layer. It consists of sheets of cells stacked upon one another;
- Dermis - the middle layer, which contains elastin and collagen fibres that provide strength to the skin as well as glands, hair follicles, blood vessels and nerves, and;
- Subcutis - the underlying fat layer.
The epidermis contains cells called melanocytes, which produce a pigment called melanin that helps to protect the skin from the effects of UV. When the skin is exposed to more UV than the melanin can block, damage occurs to the skin.
One of the skin's responses to UV light damage is to produce more melanin, which leads to a tan. However, a tan offers very little protection to repeated damage from UV light.
There are three kinds of UV light in sunlight: UVA, UVB and UVC. However, virtually all UVC light is absorbed in the upper atmosphere and does not reach ground level, while the effects on the skin of the other two types of ultraviolet (UVA and UVB) light are a little different.
UVB light is responsible for most of the symptoms of sunburn. It damages the epidermal layers of skin and the skin responds by releasing chemicals that open up the blood vessels, causing the redness, swelling and inflammation of the skin that we know as sunburn. Because it can change the genes in the DNA of skin cells, UVB exposure can lead to skin cancer.
UVA penetrates into the deeper layers of the skin. It creates damage at the level of the skin where new skin cells are formed. It also damages the elastin and collagen fibres in the dermis, leading to premature ageing. UVA exposure can also change the genes in the DNA of skin cells, potentially leading to skin cancer.
The risk of sunburn depends on how much UV light a person can be exposed to before the skin is damaged and how much UV light there is in the atmosphere.
The amount of UV light a person can be exposed to without burning varies a lot. Factors include:
- Age - babies and children are more susceptible to sunburn;
- Skin colour - fairer skin has less melanin and so is more prone to sunburn;
- The effect of some medications, which can make a person more sensitive to sunlight (such as the antibiotic doxycycline), and;
- Having a health condition that makes a person more sensitive to sunlight, such as lupus.
The amount of UV light in the atmosphere also varies considerably and this affects the time you can stay out before sunburn occurs. Factors that can increase the amount of UV include:
- The time of day - UV light levels peak during the middle of the day;
- The time of year - UV light levels are highest during summer and lowest during winter;
- Being at a high altitude - the thinner atmosphere absorbs less UV light;
- Being closer to the equator - northern areas such as Queensland and the Northern Territory have higher UV light levels than Tasmania, and;
- Environments with a lot of reflective surfaces such as water, sand and snow.
Signs and symptoms
Symptoms of sunburn can take a few hours to appear and can continue to develop for about three days.
The affected area of skin may:
- Change colour to pink or red;
- Become tender and hot to the touch;
- Become swollen;
- Be painful or itchy;
- Develop fluid-filled blisters, and;
- Peel several days after the sunburn occurred.
In a severe sunburn, symptoms may include:
- Fever or chills;
- Nausea and vomiting, and;
A tan is a sign that your skin has been damaged by UV light.
Methods for diagnosis
Sunburn can often be diagnosed by examining the skin. Your doctor may also want to know the medications you take and your medical conditions, to work out if these may affect your risk of getting sunburn. They may also ask how often you've had sunburn in the past, because multiple sunburns can increase the risk of skin cancer.
Signs that you may require treatment include:
- Fever or chills;
- A lot of pain;
- Nausea and vomiting;
- A large amount of skin involved in the sunburn, usually with blisters;
- Headache or dizziness;
- Being extremely thirsty;
- Producing no urine;
- Eyes that are sunken, sore or sensitive to light, and;
- Rapid pulse or rapid breathing.
Treatments for sunburn cannot reverse the damage to the skin caused by UV light, but they can help you feel more comfortable while the skin heals. While most cases of sunburn can be managed at home, severe sunburn may need to be treated by a doctor. Sunburn can also be related to heat exhaustion, dehydration, shock and other serious conditions that may require treatment by a doctor.
Managing sunburn at home
Drinking plenty of water can help with any dehydration caused by sun exposure.
You can manage the discomfort of sunburn by:
- Using cold compresses, or bathing the skin in cool water;
- Using a cream (for example, one that contains cortisone) or spray that helps to soothe sunburn, but not on broken skin. A pharmacist can often advise on products that may be suitable for you;
- Moisturiser to boost the skin's moisture content, if not too painful;
- Taking over-the-counter pain medications (such as ibuprofen or paracetamol) if pain is troublesome, and;
- Wearing loose, comfortable clothing that does not rub or irritate the skin.
It also helps to avoid things that could irritate the skin or cause infection while it is healing. Things to avoid include:
- Further sun exposure;
- Using soap;
- Putting butter on the skin;
- Using petroleum jelly-based products;
- Popping blisters, and;
- Picking at the skin.
Using an antiseptic cream on new skin, once the damaged skin has peeled off, can also help to avoid infection.
Skin that is damaged is more susceptible to infection. Managing sunburn symptoms correctly and not picking at peeling skin can help prevent infection.
Premature ageing of the skin
While sunburn itself does not cause premature ageing of the skin, excessive exposure to UVA light is a major cause of premature skin ageing.
Excessive UV light exposure can increase the risk of developing:
Skin cancer can develop many years after sunburn and the risk is increased by having multiple sunburns.
Sunburn symptoms often settle down within days to weeks. However, the skin damage from sunburn cannot be reversed.
Sunburn can be prevented by limiting your exposure to the sun. You can avoid sunburn by:
Avoiding the sun when UV light levels are high
Avoiding the sun during the middle of the day, when UV light levels are at their highest, can help to reduce your risk of sunburn. However, UV light levels can be high even in cool and cloudy conditions. Every day, the Bureau of Meteorology (BOM) publishes the times in your area when sun protection is advised. 
Using a broad-spectrum sunscreen
A water-resistant sunscreen with a sun protection factor (SPF) of 30, or higher, can help protect the skin from sunburn. The sunscreen should also be broad spectrum to block out both the UVA and UVB light.
For sunscreen to work most effectively, it needs to be:
- Applied generously on all exposed skin;
- Applied 20 minutes before going out in the sun;
- Reapplied every two hours, and;
- Reapplied more frequently when swimming or sweating.
To provide protection for the lips, use a lip balm with a broad-spectrum sunscreen.
Wearing protective clothing
You can reduce exposure to UV light by wearing a broad-brimmed hat that covers the face, ears and neck and clothes that cover the arms and legs. Light-coloured clothing is more effective at reflecting the light; some clothes even come with an SPF rating.
Sunglasses can help protect eyes from excessive UV exposure, which has been linked to increased risk of eye conditions such as cataracts, macular degeneration, pterygium and some cancers of the eye and eyelids.
Wrap-around styles offer the most protection and it is important to know that just because the lenses of a pair of sunglasses are dark does not mean that they offer protection from UV light. Sunglasses that meet the Australian Standard AS1067 offer effective protection from UV light.