By Maren Dunn, D.O. Explorebigsky.com Health Writer

My roommate had an allergic reaction a couple of weeks ago but can’t pinpoint what it is. Should she carry an epi-pen?

Allergic reactions can cause a wide spectrum of symptoms, from itchy skin to life-threatening breathing problems. Sometimes the allergen responsible is easy to identify, other times not. What’s most important to understand is the difference between mild allergic symptoms versus life-threatening symptoms so proper treatment can be administered as quickly as possible.

Most allergy symptoms are caused by the immune system’s hypersensitivity to a normally harmless substance. What happens is this: IgE antibodies (produced by the immune system) recognize the substance, and then trigger other blood cells to dump their contents, including histamine. This cascade manifests as symptoms wherever it takes place, such as the skin or the airways.

When a mild allergic reaction occurs in the skin, itching, hives, flushing and swelling are common reactions. If the skin involved is the lips or oral mucosa, swelling in this area is called angioedema and can be a sign of a more serious situation. When the reaction is in the respiratory tract, sneezing, nasal congestion and itchy mouth are common. More serious respiratory reactions include wheezing, shortness of breath or choking. The mild symptoms can often be managed with over-the-counter medications, while the more serious ones should be treated and monitored by a medical provider.

In anaphylaxis, a life-threatening full-body allergic reaction, many systems become involved, including the cardiovascular and neurologic systems. Anaphylaxis manifests with many of the above symptoms, and also a fast heart rate, dizziness or passing out, nausea, vomiting or a sense of impending doom. Immediate treatment with epinephrine is mandatory.

Since some cases require additional treatment to stop the reaction, people with anaphylaxis should seek medical attention immediately, even if they have already self-medicated with an epi-pen.

If you have suffered an allergic reaction of any kind, it’s important to discuss it with your medical provider, who can determine what treatment is appropriate for you, and whether it’s necessary for you to carry an epi-pen.