Praise be to Allah.
Putting on perfume after doing ghusl when entering ihraam is Sunnah, because the Prophet (peace and blessings of Allaah be upon him) put on perfume for his ihraam. ‘Aa’ishah (may Allaah be pleased with her) said: I put perfume on the Messenger of Allaah (peace and blessings of Allaah be upon him) for his ihraam before he entered ihraam. And the glistening of the musk could be seen in the parting of his hair when he was in ihraam. End quote.