I have never used Primatene Mist for a serious allergy (anaphylaxis), but I believe it would be effective. After December 31, 2010 it will no longer be sold, so you may want to stock up now. Prescription rescue inhalers work similarly (albuterol, Proventil, Ventolin, Alupent). The reason we use inhalers for asthma (instead of pills) is to avoid the side effects such as rapid heart rate and elevated blood pressure, which you’ve probably experienced if you’ve ever used your Epi-Pen. If I were to use Primatene for an acute reaction, I would also use an antihistamine such as Benadryl. Repeating the dose in 3 to 6 hours may also be necessary. Certainly if the choice is dying or using Primatene, I would keep the Primatene handy. Taking an antihistamine before probably exposure (such as working outside) might also lessen an allergic response.