During Umrah and Hajj is it allowed to wear ‘niqab’?.

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

It is forbidden for a woman in a state of Ihraam for Hajj or ‘Umrah to wear Niqab (face covering) as the Prophet said: “A woman in a state of Ihraam should not cover her face or put on gloves”. [Al-Bukhari].

However, if she needs to cover her face because non-Mahram men are passing near her or they are where she is, then, in this case, she should lower her head-covering over her face as ‘Aa’ishah said: “Men on camels (or on horses) would pass by us while we were in the state of Ihraam with the Prophet so, when they were near us, we would cover our faces with our head-covering and when they passed us, we would uncover our faces again”. [Abu Daawood]

Allah knows best.