ASALAOMOALAIKUM
it is to say that ...niqab is obligatory/ compulsory for every muslim women who performz hajj and umra ...yes indeed it is not allowed in the islamic shariah that no cloth should touch the face of muslim women but the shariat never said that women are allowed to not hide their face ....if u see the women of saudia arabia performing hajj and umra u will clearly see that they hang a piece of cloth which does not touch their face. So from where i studied it is obligatory for a women to use that cloth to hide her face.
jazakullah