Sunburn
Sunburn is when you stay outside in the sun too long. It was introduced with Seasons and if you have Bon Voyage you can get a sun burn 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 subathing on the beach.
When a Sim gets a sunburn, its face and portrait turns red.