Muco vs. moccio
While both muco and moccio refer to nasal secretions, the choice between them depends entirely on the context and tone. Muco is the formal, biological term, whereas moccio is the colloquial, informal word for snot.
Muco
B1Muco is the standard, scientific, and polite term for mucus. It refers to the biological substance produced by mucous membranes. You should use muco in medical situations, formal descriptions, or when you want to discuss the symptom without being vulgar. It can refer to mucus in the nose, throat, or lungs.
Il dottore mi ha prescritto uno sciroppo per sciogliere il muco.
(The doctor prescribed me a syrup to loosen the mucus.)
Il muco serve a proteggere le vie respiratorie dai batteri.
(Mucus serves to protect the respiratory tract from bacteria.)
Ho molto muco in gola e non riesco a deglutire bene.
(I have a lot of mucus in my throat and cannot swallow well.)
L'analisi del muco nasale può rivelare un'infezione.
(Analysis of the nasal mucus can reveal an infection.)
Quando tossisco sento che c'è del muco nei bronchi.
(When I cough, I feel that there is mucus in my bronchial tubes.)
Moccio
B2Moccio is the informal, everyday word equivalent to snot. It usually refers specifically to the runny, viscous substance coming out of the nose. It is often used in contexts involving children, crying, or messy colds. While not an obscenity, it is considered a gross or childish word rather than a medical one.
Il bambino piangeva così forte che gli colava il moccio.
(The child was crying so hard that snot was dripping down.)
Pulisci quel moccio con un fazzoletto, è disgustoso!
(Wipe that snot with a tissue, it's disgusting!)
Aveva una candela di moccio che gli pendeva dal naso.
(He had a trail of snot hanging from his nose.)
Non pulirti il moccio sulla manica della maglietta.
(Don't wipe your snot on your t-shirt sleeve.)
Sei pieno di moccio, vai a soffiarti il naso.
(You are full of snot, go blow your nose.)
Summary
Use muco when speaking to a doctor, discussing health formally, or referring to the biological substance in the chest or throat. Use moccio when referring to snot dripping from the nose, especially regarding children or in casual, humorous, or gross descriptions.