What is Brachycephalic Obstructive Airway Syndrome

Which breeds are affected by BOAS?

Brachycephalic Obstructive Airway Syndrome (BOAS) is a respiratory condition affecting flat-faced (brachycephalic) breeds like Pugs, French Bulldogs, and English Bulldogs. It's characterised by breathing difficulties due to narrowed airways caused by the breed's skull conformation.   

This leads to various issues, including:    

• narrowed nostrils: the nostrils are often constricted, making it harder for air to enter the nasal passages.  

• elongated soft palate: the soft palate at the back of the mouth can be too long, blocking the entrance to the windpipe.  

• narrowed windpipe: the windpipe itself can be narrower than in other breeds.  

• everted laryngeal saccules: in some cases, tissues inside the larynx (voice box) can be pulled into the airway, further obstructing airflow.  

Written by Dr. Mariella Roberts, Veterinary Surgeon, Animal Trust Vets CIC | Published August 2025 | Review date August 2027 | This advice is for UK pets only and is not a replacement for seeing a vet