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 (may Allah be pleased with him) to wear a silk shirt while travelling because of an itch he used to feel on his body, and Sayyiduna al-Zubayr bin al-Awwam (may Allah be pleased with him) as well.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الخوف / 6077