A pronounced puffy swelling of the head, especially the muzzle and around the eyes, is called angioneurotic edema. This swelling is often very disturbing to the owner but rarely causes serious repercussions. Insect bites, bee stings, and spider bites are the most common causes. Treatment with corticosteroids and antihistamines is required for a quick response.
The most severe allergic reaction is called anaphylactic shock. Vomiting, diarrhea, and difficulty breathing can be followed by coma and death, usually within 15 minutes. Although very rare, it is most commonly caused by a reaction to a vaccination. Other causes include bee or wasp stings. Treatment requires immediate administration of adrenalin and antihistamine intravenously.