Thank you for your query at AskTheDoctor.com
I understand your concern.
This seems more like an allergic rash as the picture doesn't really show your bumps very clearly. However, if it's getting worse when hot, it most likely is urticaria because of the heat.
You need to take Tab. Claritin 10 mg once daily for 3 days at bedtime and apply Mupirocin ointment twice daily on the bumps with pus. It will definitely resolve. Additionally even calamine lotion will be helpful. You can share a higher resolution image or a better picture showing the bumps clearly.
Hope this was helpful,
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