When a woman wears perfume, the ruling depends on the situation: 

1 –  

Using perfume for the husband. 

This is mustahabb and recommended, because it is part of treating him kindly, and it helps to increase love between the spouses, when each of them pays attention to what the other likes. 

Al-Mannaawi said in Fayd al-Qadeer (3/190): 

As for putting on perfume and adorning herself for her husband, it is required and is something that is liked. One of the wise men said: For a woman to adorn herself and put on perfume for her husband is one of the strongest causes of love and affection between them, and wards off dislike and disdain, because the eye is the pioneer of the heart; if the eye looks at something attractive, the message will reach his heart and love will be created, but if it looks at something ugly or that it does not like of outfits or garments, that that message will reach the heart and dislike and disdain will be created. Hence the advice that Arab women gave to one another was: Beware of letting your husband see anything that does not please him or letting him smell anything from you that he finds off-putting. End quote. 

2 –  

Putting on perfume and going out with the aim of letting non-mahram men smell it. This is haraam, and is a major sin. 

It was narrated from Abu Moosa (may Allaah be pleased with him) that the Prophet (peace and blessings of Allaah be upon him) said: “If a woman puts on perfume and passes by people so that they can smell her fragrance, then she is such and such,” and he spoke sternly - meaning an adulteress. Narrated by Abu Dawood (4173) and al-Tirmidhi (2786); classed as saheeh by Ibn Daqeeq al-Eid in al-Iqtiraah (126) and by Shaykh al-Albaani in Saheeh al-Tirmidhi. 

al-Mannaawi said in Fayd al-Qadeer (1/355): 

“She is an adulteress” means: because of that she is exposed to zina, and implementing the means that lead to it and calling those who seek it. Hence she is called an adulteress in a metaphorical sense, because desire may prevail and real zina may take place. Her passing by men is likened to her sitting in their path so that they pass by her. End quote. 

3 – 

If she puts on perfume and goes out, and thinks it most likely that she will pass by a group in which there will be men who will smell her perfume and fragrance, this is also haraam, even if she does not intend to tempt men and that is not her aim, because this action is a fitnah (temptation) in and of itself. There is also an indication in sharee’ah that it is haraam and not allowed. 

Allaah says (interpretation of the meaning):  

“And tell the believing women to lower their gaze (from looking at forbidden things), and protect their private parts (from illegal sexual acts) and not to show off their adornment except only that which is apparent (like both eyes for necessity to see the way, or outer palms of hands or one eye or dress like veil, gloves, headcover, apron), and to draw their veils all over Juyoobihinna (i.e. their bodies, faces, necks and bosoms) and not to reveal their adornment except to their husbands, or their fathers, or their husband’s fathers, or their sons, or their husband’s sons, or their brothers or their brother’s sons, or their sister’s sons, or their (Muslim) women (i.e. their sisters in Islâm), or the (female) slaves whom their right hands possess, or old male servants who lack vigour, or small children who have no sense of feminine sex. And let them not stamp their feet so as to reveal what they hide of their adornment. And all of you beg Allaah to forgive you all, O believers, that you may be successful”

[al-Noor 24:31]

So women are forbidden to show their adornments to non-mahram men, and perfume is undoubtedly one of the woman’s adornments, so it is included in this prohibition. 

And it was narrated that Zaynab, the wife of ‘Abd-Allaah ibn Mas’ood, said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said to us: “If one of you attends the mosque, let her not put on perfume.” Narrated by Muslim (443). 

If the Prophet (peace and blessings of Allaah be upon him) forbade women to go out to the mosque wearing perfume, because men will usually smell some of the fragrance because of close proximity and there being no barrier between men and woman, then it is more likely that women are not allowed to go out to the marketplace and gatherings wearing perfume, although it is not regarded as a major sin, rather it is something that is clearly haraam.  

Ibn Hajar al-Haytami said in al-Zawaajir ‘an Iqtiraab al-Kabaa’ir (2/71-72): 

The ahaadeeth which count it as a major sin should be interpreted as meaning that this applies if the fitnah is certainly there; when there is merely the fear of fitnah, then it is makrooh, or when she thinks it will cause fitnah then it is haraam but is not a major sin, as is obvious. End quote. 

See also the answer to question no. 7850 

4 – 

When she puts on perfume and thinks it most likely that her fragrance will not reach people and that men will not smell any of it, such as if she is going out in her husband’s car on a trip to an isolated place, or to visit her family, or she is going out in her husband’s car to a gathering for women only, or she is going to the mosque in the car and she is going to get out at the entrance to the prayer-hall that is for women only and is completely separate  from the men, then she is going to come straight back in the car without walking in the street, and other such situations where the woman does not expect to pass through the streets and her aim in putting on perfume is to keep herself clean in general as enjoined by sharee’ah. In that case there is nothing wrong with her using perfume, because the reason for the prohibition, which is that the fragrance might reach other men, does not apply. 

The evidence for that is as follows: 

(i)The apparent reason for the prohibition in the evidence quoted above does not apply in this case, so there is no fitnah and there is no provocation of desire.

(ii)In Sunnah there is an indication that the womenfolk of the Sahaabah used to use perfume when they thought it most likely that it would not be smelt by men.

It was narrated that ‘Aa’ishah (may Allaah be pleased with her) said: We used to go out with the Prophet (peace and blessings of Allaah be upon him) to Makkah, and we would apply perfume to our foreheads when entering ihraam, then if one of us sweated it would run down her face, and the Prophet (peace and blessings of Allaah be upon him) would see it but he would not rebuke her. 

Narrated by Abu Dawood (1830) and classed as hasan by al-Nawawi in al-Majmoo’ (7/219) and as saheeh by al-Albaani in Saheeh Abi Dawood. 

This is to be understood in the light of the conditions that were known in earlier times, when the caravan of women was separate from that of men, or the woman would be in her howdah and did not mix with men or pass by the places where they were. 

Shaykh ‘Abd al-‘Azeez ibn Baaz (may Allaah have mercy on him) said in Majmoo’ al-Fataawa (10/40): 

It is permissible for her to apply perfume if she is going out to a place of women and is not going to pass by men in the street. End quote. 

It says in Jalasaat Ramadaaniyyah (1415/al-Majlis al-Khaamis/Majmoo’at As’ilah tuhimm al-Usrah) by Shaykh Ibn ‘Uthaymeen (may Allaah have mercy on him): 

But if the woman is going to ride in the car and her fragrance will only be apparent to those before whom she may show the fragrance, and she will exit the car and go straight to her workplace without there being any men around her, then there is nothing wrong with it, because there is nothing haraam involved. When she is in her car it is as if she is in her house. But if she is going to pass by men then it is not permissible for her to wear perfume. End quote. 

If an emergency arises in which some men happen to smell the perfume of this woman, because of a car accident, for example, or a sudden illness because of which she is taken to the hospital and the like, then this is something that is forgiven, in sha Allah, because Allaah does not burden any soul beyond its scope and the shar’i ruling is to be followed in cases where one has the choice, not in cases of necessity. 

And Allaah knows best.