Sahih Muslim Book 24, Hadith Number 5170.

Chapter : It is permissible for a man to wear silk because of itch or some other reason.

Anas reported that Allah’s Messenger (may peace be upon him) granted concession, or Zubair b. Awwam and ‘Abd Al-Rahman b. Auf were granted concession, for the wearing of silk because of the itch that they both had.