How effective are steroids for treating croup?

Croup and steroids: Oral steroids can be very helpful in reducing the severity of upper airway edema associated with croup, but is generally reserved for those children who have severe symptoms such as stridor at rest. Steroids treat symptoms, not the cause, and should be used sparingly in growing children.

Yes, moderate/severe: Croup is an infection (typically viral) of the voice box (larynx) and windpipe (trachea). Characterised by a barking cough, hoarse voice and noisy breathing. It is most common in young children as their airways are narrow and more prone to swelling. In moderate or severe croup (stridor and increased rate and work of breathing) a child may be treated with oral Dexamethasone to settle the swelling