Are the waste, blood, and carcasses of lice, mosquitoes, and small insects that feed on human blood considered impure if abundant? And what are the sayings of the people of knowledge regarding this issue?

There is a difference of opinion regarding the droppings of mice: are they impure if abundant, or not? The madhhab of Imam Ahmad and a group of the Salaf, and one view among the Shafi'is, is that they are pure. The second opinion is that they are impure and must be washed. A person afflicted with obsessive-compulsive disorder (waswasa) is advised to follow the first opinion (purity) because it is strong in its evidence and more lenient for them, as it is permissible for someone with waswasa to take the easier opinions to remove hardship and alleviate difficulty.