It is disliked for a fasting person to use incense, oud, amber, or anything else that has a substance, as it exposes the fast to danger. If it is confirmed that something enters the throat due to his action, his fast is invalidated. However, if it enters without his doing, it does not invalidate the fast because it is unavoidable. The use of perfumes during the day in Ramadan by a fasting person does not invalidate the fast, as they are merely scents that cling to the air without substance, so they do not invalidate the fast, like musk.