Alar botox is an alar base reduction to decrease the nostril flaring and / or decrease the overall size of the nostrils. Nasal flare when smiling is normal, but if it is excessive, this should be improved with Botox, a temporary solution. Botox improves the dynamic action of nostril flaring, not static nostril flaring.
There are muscles that pull the nasal tip down and pull the nostrils laterally. By injecting a few units of Botox into specific areas around the nose, the pull of these muscles will be softened, reducing the nostril flare.
Each injection would only need two to three units, a small amount, making this option the cheapest solution. Botox would need to be repeated twice or three times a year.