Drink Water
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"Bad sunburns cause a process called vasodilation, where your blood vessels dilate and you lose water from your skin very quickly," says Bowe. "This can lead to dehydration, fatigue, and even heat stroke if not treated." Start sipping water immediately, and keep drinking it to be sure you stay hydrated. "Coconut water or other waters with added electrolytes can be even more effective at preventing dehydration," Bowe adds.