Question: In some of the pharmacies (they sell) inhalers which some of the asthma sufferers use; is it permissible for the fasting person to use it during the day in Ramadan?
A: The use of the inhaler by the one who is fasting is permissible whether his fast is in Ramadan or other than Ramadan.
That is because the particles in the inhaler do not reach the stomach, rather they reach the lungs and cause them to open up thereby allowing the person to breathe normally.
So, it is not regarded as food nor drink, and that which is known is that the basic principle is the validity of the fast (is maintained) until (authentic) evidence from the Book, or the Sunnah, or consensus (ijmaa’) or valid juristic reasoning (qiyaas) indicates otherwise.
– Shaykh Ibn ‘Uthaymeen, Fataawa Ramadan – Volume 2, Page 531, Fatwa No.502 Fataawa Ibn ‘Uthaymeen – Volume 1, Pages 169-170