It is permissible, as far as Islamic Shari`ah is concerned, to use an inhaler for asthma patients while fasting. The inhaler provides only some moisture and it does not involve taking in of any food or liquid through the mouth.

Sheikh Ahmad Kutty, a senior lecturer and Islamic scholar at the Islamic Institute of Toronto, Ontario, Canada, stated,

According to the preferred view of scholars, using inhalers by asthma patients does not break their fast. The drug inside an inhaler, we are told, goes straight into the airways; while the airways are treated, very little of the drug itself gets into the rest of the body. This being the case, it is perfectly comparable to rinsing the mouth with water or gargling, brushing the teeth, or using eye or ear drops; such actions should never be reckoned as consumption of foods or drinks.

Therefore, you may use them if need be. Rules of Islam, we may do well to remember, are not at all intended to make life hard for people. Almighty Allah says in the Qur’an, [He [Allah] has imposed no difficulties on you in religion] (Al-Hajj 22:78).