Brief Answer:
Steroids have advantages

Detailed Answer:
Hi,

First of all it is not clear whether the reason for croup is bacteria or virus. If there are declining oxygen saturation then the doctors would put a baby on steroids.
Steroids need not be given all the time for a confirmed case.
If it is bacteria, oral antibiotics are sufficient as long as the Spo2 values are good. If it is virus, maintenance treatment is given. It is mainly inhaled vapor therapy, putting humidifier in the room, giving steam based bath. This helps the secretions in the airway humid.
So the introduction of steroids is mainly on the basis of the nature of symptoms.
Few good studies analysed and revealed that steroids (oral corticosteroids) reduce symptoms and re-admissions to emergency departments, shortened hospital stays, and also reduce the need for treatment with epinephrine at a later date.

Hope this is clear why steroids are given and they are not always necessary.

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