Short answer
Kohl made from ithmid (antimony) is allowed for men and women, and the Prophet ﷺ praised ithmid for the eyes, so many scholars count it a sunnah. The Hanafi texts allow ithmid for men and dislike black kohl only when a man wears it purely as a beauty look. Kohl does not affect wudu or break the fast.
Applying ithmid is permissible for men by agreement, and it is a sunnah when done for the eyes and to follow the Prophet ﷺ. The Hanafi scholars agree that black kohl is makruh for a man when his aim is only adornment, and most see no harm when it is not. For women it is a permitted adornment.
The four schools agree on this.
Explanation
Ibn Abbas reported that the Prophet ﷺ said the best kohl is ithmid, because it clears the sight and makes the lashes grow. Ithmid is a natural antimony stone, ground into a fine powder and applied with a thin stick along the inner rim of the eye. In South Asia it is called surma, and kajal is a similar dark paste.
For men. The Hanafi books say there is no harm in ithmid for men, and many scholars count it a sunnah because of this hadith. Make your intention the health of your eyes and following the Sunnah. The Hanafi scholars agree that black kohl is disliked for a man when he wears it only as a beauty look, and heavy eyeliner styled like women's makeup falls under men wearing makeup. Many people apply it at night before sleeping, though the hadith scholars differ over the chains of the reports that fix three strokes in each eye.
For women. Kohl is a lovely adornment. Like other makeup, a striking look is for her husband, other women and mahrams; see is wearing makeup haram.
Purity and fasting. Kohl does not leave a layer that stops water, so wudu and ghusl are valid with it on. In the Hanafi school it does not break the fast, even if you taste it in your throat; see what breaks your fast. The four schools agree that kohl is allowed.
Safety. Some kohl and kajal sold online has been found to contain lead. Buy from a trusted seller, since harming your eyes defeats the purpose.
The evidence
Quran, Surah Al-A'raaf 7:32
قُلْ مَنْ حَرَّمَ زِينَةَ ٱللَّهِ ٱلَّتِىٓ أَخْرَجَ لِعِبَادِهِۦ وَٱلطَّيِّبَٰتِ مِنَ ٱلرِّزْقِ ۚ قُلْ هِىَ لِلَّذِينَ ءَامَنُوا۟ فِى ٱلْحَيَوٰةِ ٱلدُّنْيَا خَالِصَةًۭ يَوْمَ ٱلْقِيَٰمَةِ ۗ كَذَٰلِكَ نُفَصِّلُ ٱلْءَايَٰتِ لِقَوْمٍۢ يَعْلَمُونَ ﴿٣٢﴾
Say, "Who has forbidden the adornment of Allah which He has produced for His servants and the good [lawful] things of provision?" Say, "They are for those who believe during the worldly life [but] exclusively for them on the Day of Resurrection." Thus do We detail the verses for a people who know.
Lawful adornment and care of the body are allowed to believers.
Sunan Abi Dawud 3878
Graded sahih... وإن خير أكحالكم الإثمد يجلو البصر وينبت الشعر ...
"The best kohl you use is ithmid: it clears the sight and makes the hair grow."
The Prophet praised ithmid kohl, which is why many scholars call it a sunnah.
Where the ruling is recorded
- al-Fatawa al-Hindiyya, Kitab al-Karahiyya, chapter on adornment. No harm in ithmid for men by agreement; black kohl is disliked by agreement when the aim is adornment, and the scholars differ when it is not.
- al-Durr al-Mukhtar with Radd al-Muhtar, Kitab al-Sawm, chapter on what does and does not break the fast. Kohl does not break the fast even if its taste reaches the throat.
Checked by our team. For a more accurate answer to your own situation, consult a scholar. Quran translation by Sahih International. Hadith Arabic from the standard editions of the six books and the Muwatta, with gradings as recorded there; the English is our own rendering. Spotted a mistake? Tell us.