What Are the Symptoms of an Allergic Reaction?

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  • Written By: Madeleine A.
  • Edited By: W. Everett
  • Images By: Pilotl39, Kitch Bain, Greg Friese, Alekss, Lovrencg
  • Last Modified Date: 25 October 2018
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Symptoms of an allergic reaction can take place locally or systemically. Symptoms of a localized allergic reaction are redness, inflammation, and localized itching. Symptoms of a systemic allergic reaction include difficulty breathing, facial, tongue or throat swelling, wheezing, and chest pain. These symptoms can be life threatening and require immediate medical intervention.

Other symptoms of an allergic reaction include nausea, vomiting, diarrhea, irregular heart beat, and even unconsciousness. Treatment for symptoms of an allergic reaction depends upon the severity of the symptoms and what the offending allergen is. Mild allergic reactions respond well to over-the-counter oral or topical antihistamines.

If the individual experiences severe symptoms of an allergic reaction, he needs emergency medical care, such as intramuscular or intravenous epinephrine. Causes of an allergic reaction include bee stings, medications, foods, and animal dander. In addition, allergic reactions can occur as a result of hay fever and exposure to pollen, grass, and molds. Peanut allergies can be especially severe, as even a minute amount of a peanut or byproduct can cause dangerous reactions.

Anaphylaxis is a life-threatening and rapid allergic reaction that occurs soon after the person is exposed to the allergen. If not treated, the person can die in as little as 15 minutes. People who are allergic to bee venom are often advised to carry an EpiPenĀ®, which is a pen-like device filled with epinephrine. Injecting oneself with epinephrine after an allergic reaction can usually prevent serious complications.


Occasionally, the allergist will recommend that the patient receive routine allergy shots. These are sometimes administered on a weekly basis to prevent symptoms of an allergic reaction in patients who are sensitive to certain substances. In addition, allergy medications can be taken on a daily basis and are available over the counter. People should not take these medications unless they are under the direct supervision of an experienced health care provider.

Sometimes, even people who are insensitive to allergic reactions can experience mild effects from certain substances, which may include new laundry detergents or soaps. These reactions are typically mild and are generally quickly resolved when the substance is removed or washed off. To further reduce the effects of these allergens, the individual can dab on an over-the-counter antihistamine, which is generally effective in relieving itching, redness, and swelling.

It is important to note that even if a person has never experienced allergic reactions in the past, he should seek a medical evaluation if he exhibits symptoms of an allergic reaction. Although allergies usually present themselves during childhood, they sometimes do not become evident until adulthood, or even very late in life. Physicians may recommend these patients see an allergist who can perform sensitivity tests to determine what they may be allergic to.



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