Rash all over arms and legs after doing IPL only on my legs??

2 weeks ago I did my first IPL hair removal treatment on my legs, and a week ago I started developing a bad rash (tiny red bumps) all over my legs, and just 2 days ago the same rash (but slightly milder) started appearing on my arms. I've tried anti-histamines, aloe vera gels and putting wet cloths on my legs but they aren't helping much. Any idea what this is and how I can prevent this?

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