Allergy reactions - Danger!
Is there any trouble breathing, dizziness, tongue swelling, mental confusion, generalized hives?
The standard of care is the prompt administration of epinephrine [also called Adrenaline] in the muscle (IM) in the appropriate dose and calling 911 for immediate transport to an emergency medical facility. Oxygen and IV fluids may be indicated. In hypotensive (near or in faint situations), the patient should be placed in a supine (on the back) position with their toes higher than their nose. Although typically used, antihistamines and steroids don't work quickly enough to alter the course of an immediate allergy reaction. It may come as a surprise but, there's no evidence-based support for their use.
The detailed steps for standard of care are described in the "Practice Parameter On Anaphylaxis" developed by the Joint Task Force of the American Academy of Allergy, Asthma & Immunology or the AAAAI), the American College of Allergy, Asthma & Immunology (ACAAI), and the Joint Council of Allergy, Asthma and Immunology (JCAAI). These documents are published online and in print [Lieberman P. et al. J Allergy Clin Immunol. 2010;126:477-480].
Note: Even after successful treatment, however, there remains a risk for further, significant anaphylactic reactions, even 4-8 hours later that demand additional treatment and supportive care. Thus, proper and well-equipped observation is highly recommended.
See also, The Food Allergy and Anaphylaxis Network