ANSWER:

Athan has nothing to do with answering the call of nature. You can enter the washroom whenever you want to whether the athan is going or not! What is prohibited is to answer the athan or making dhikr etc.

Is it allowed for a person to go to the bathroom when the athan is going on(whether to relieve oneself, just do wudu or for other reasons)? Is there evidence for prevention of this?

Halal/Haram Matters, Innovations |