Q: Is it permissible for the fasting person to smell perfume and ʿoūd [type of incense]?

A: Shaykh ʿAbd al-ʿAzīz ibn Bāz: One should not inhale ʿoūd. There is no problem with [smelling] the other types of perfumes, except bukhūr [incense]. As for ʿoūd itself, it should not be inhaled because some of the people of knowledge say that if ʿoūd is inhaled it breaks one’s fast. This is due to some of its elements going to the brain [therefore affecting the fast]. It also actively spreads [throughout the body]. But smelling it unintentionally does not break one’s fast.

Commentary of Ustādh Mūsá Richardson: Important cultural note for those who do not know: In the Arab lands, it is a common practice in gatherings to pass around the ʿoūd [a type of incense] burner, and each person would take his shimāgh [headwear] and make like a quick “facial sweatlodge” [for lack of better words] by wrapping his headwear around the incense burner for a moment. With this kind of intensity, the smoke is inhaled in a way that is similar to how cigarettes are smoked. This is important to know, so that some of us do not believe it to be impermissible to burn incense while fasting or smell it, or that it breaks the fast. What breaks the fast is inhaling it intensely, just like if you put your face over a pot of steaming food and inhaled over and over again. In such a case, you would find that you have actually ingested something from the steam. So it is permissible to smell incense in the room, or food, or any other thing, so long as you do not inhale and ingest it. The fatwá quoted should be understood based on this, and Allāh knows best.

Source: حكم شم الصائم رائحة الطيب والعود
Translated by: Munīb al-Ṣumālī