it is the first remedy to think of for any frightening event, something that is so scary that your heart pounds and you wonder if you will survive. Think of Aconite as the first remedy after a dog fight - for you and your dog - or after any kind of scary physical or emotional trauma.
Aconite is also a remedy to think of for high fevers or other illness that comes on after exposure to a cold wind. For example, you are at an agility competition outdoors where there is a stiff chilly breeze. The next day your dog has a red, swollen, painful ear, or a fever with a hoarse dry cough - Aconite is the remedy.
For acute cases like those described above, a 30C potency might be sufficient. You can give the remedy dry or wet (one dose dissolved in a glass of water, giving 1/2 teaspoon doses) every hour or so for three or four doses.
Remember, with homeopathic remedies don't dose more than necessary to bring about a change in the symptoms. Once that happens, stop dosing and let your pet's body adjust to the new state of affairs.
In chronic cases, such as a dog who has never recovered from a frightening event, or who was severely traumatized in the past - for example, dogs who develop severe anxiety at the dog park after being attacked there, or storm phobia that develops after being caught outside in a storm, or dogs who have been through the rescue experience and are still traumatized - higher potencies might be necessary. Remember, with higher potency - stronger - remedies, dose less frequently and think twice before repeating the dose.