Answered by Shaykh Rami Nsour
Question: Is it permissible to swallow saliva and mucous in the Maliki School?
Answer: Mucous and saliva are pure (tahir) and therefore you can swallow them. While one is fasting though, it is mentioned that to swallow mucous disliked but not break the fast according to the relied upon (mu’tamad) opinion. There is another opinion that swallowing mucous that one is able to spit out would actually break the fast. [Mukhtasar Khalil]