Musnad Ahmad 3:99

Sufyan narrated to us, from Ayyub ibn Musa ibn ‘Amr ibn Sa‘id, from Nabih ibn Wahb, a man from the Banu ‘Abd al-Dar (the chamberlains), from Aban ibn ‘Uthman, that he narrated from ‘Uthman: That the Messenger of Allah (peace and blessings of Allah be upon him) granted a concession—or he said: regarding the one in ihram—if his eye is ailing, that he may dress it with aloe (sabir).