Sayyiduna Anas bin Malik (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) permitted Sayyiduna Abd al-Rahman bin Awf and Sayyiduna al-Zubayr bin al-Awwam (may Allah be pleased with them both) to wear silk shirts because of itching.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6074