Sunburn

Sunburn occurs when Sims stay outside in the sun too long. It was introduced with Seasons and if you have Bon Voyage you can get a sunburn on Twikkii Island. This can easily be resolved by putting on sunscreen: in Bon Voyage just take it with you in your inventory. It can also occur from prolonged exposure to the sun from sunbathing on the beach.

When a Sim gets a sunburn, their face and portrait turns red. Sometimes if your sim is in the sunburnt position for too long they will faint and will have suffered heatstroke. This can be resolved in 2 ways:
 * Your sim can wait for nightfall, where they will cool down.
 * Another sim may bring a glass of water to them, and tip it over them. This cools your sim down.

You can avoid heatstroke by cooling your sim down once they start over-heating. Give them some lemonade, get them indoors or in the pool, you should probably not put them in the hot tub though.

After around 3 days, the sunburnt Sim will revert to normal. If it doesn't revert, then you are experiencing a known bug and the Sim in question will remain burnt forever. The only known remedy is to download a hack.