Can you make your Wudu over oil-based cosmetics such as kohl and lipstick or does it need to be removed first? Does this apply to kohl al Hajar too?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

There is no harm for a woman to use any kind of beautification materials and cosmetics such as lipstick, Kohl and so on, as long as they are of pure materials and do not constitute a form of imitation of non-Muslim women. But if the cosmetics could be a barrier that prevents water from reaching the skin, it becomes necessary to remove them before performing ablution or Ghusl (ritual bath).

For more benefit on the nullifiers of ablution, please refer to Fatwa 84093.

Allah knows best.