How do I treat a severe mosquito bite allergy?

Mosquito repellent. First, protect yourself from getting stung - insect repellents, wearing long sleeves, etc. Once stung, apply ice, prescription-strength topical steroid and an antihistamine such as Cetirizine 10mg (zyrtec) or fexofenadine 180mg (allegra). First aid calamine with pramoxime lotion mixed with Hydrocortisone 1%. Next step - see an allergist for consideration of desensitization (allergy shots).