Musannaf Ibn Abi Shaybah

A man asked Hazrat Ibn Abbas (may Allah be pleased with them both) while he was in the state of Ihram for Hajj, "Can I scratch my head while in Ihram?" Hazrat Ibn Abbas (may Allah be pleased with them both) joined both his hands together and scratched his head with them and said, "In any case, this is what I say." The man asked, "What if you kill a louse?" He replied, "Distance be upon you! A louse is not an obstacle to scratching my head, and indeed, you people have only been prohibited from hunting during Hajj."