Reference: Fataawa Ramadhaan – Volume 2, Page 531, Fatwa No.501
Fataawa Ibn ‘Uthaymeen – Volume 1, Pages 500-501
Question: Does the use of an asthma inhaler break the fast?
Response: The response to this question is that the inhaler which you use vaporises and [as such] does not reach the stomach.
Therefore, we say, there is no harm in using this inhaler whilst you are fasting, and it does not break the fast because, as we have said, it’s particles do not enter the stomach since they vaporise and disperse. [Since] none of the particles enter the stomach we cannot say that it[‘s use] necessitates the breaking of the fast, so it is permissible for you to use it whilst fasting and your fast is not invalidated by it.
