If someone injures themself (in this case, typically a burn from carpet, grass or perhaps trampoline) and your body reacts to it in a bad way, you can get reactive acne. It’s a type of acne that spreads like a rash along your legs or arms (depending where you had the injury). If you see a case of reactive acne appearing anywhere else on your body, it is NOT normal. Please go see a doctor, or make sure it’s definitely reactive acne first.
Reanna fell on the trampoline and scraped her knee. Therefore, reactive acne spread across all her legs.