How long it takes to get sunburnt depends on many factors, the biggest ones being your skin type and how much time you spend in the sun. People with lighter skin burn more easily and have a greater risk of developing skin cancer, so they need to be careful in the sun. But even those with darker skin can get sunburnt - it may just look itchy or tender rather than change colour. The intensity of the sun is also important - it’s more intense near the equator and UV rays penetrate light clouds – so you can still be at risk on cloudy days, especially in winter.
Overexposure to the sun’s rays causes your body’s natural defences to become overwhelmed, which results in a sunburn. The inflammatory response that kicks in usually starts four to six hours after the initial exposure and can take longer in some cases. This is why your grandmother’s use of ice cubes to relieve itching from sunburn doesn’t work – the inflammatory process is already happening and there is nothing ice can do to prevent this from occurring.
Once you’ve gotten a sunburn, the most important thing to do is get out of the sun and cover any exposed skin. A cool bath or shower, or applying a cold compress to the skin, can help ease pain and swelling. Ibuprofen or acetaminophen can be taken to reduce pain and inflammation, and hydrocortisone cream can be used on itchy, inflamed areas. It is also important to drink plenty of water, both right away and for a few days after to avoid dehydration.