What Is an Acute Allergic Reaction?

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  • Written By: S. Reynolds
  • Edited By: Jenn Walker
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  • Last Modified Date: 20 October 2016
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An acute allergic reaction occurs when the body reacts to a certain substance by releasing histamines. Signs of an acute allergic reaction include sneezing, a runny nose, rashes, swollen skin, hives, and difficulty breathing. The symptoms often commence within minutes after exposure. An acute allergy attack may occur when one is exposed to common allergens such as pet dander, shellfish, peanuts, wheat, and dairy. A sudden, severe allergic reaction can be fatal for the person having the attack.

Some people are genetically predisposed to having acute allergy attacks. Early exposure to certain allergy-causing substances can cause someone to develop severe, lifelong allergies against it. The genetic component is clear, however, as allergies tend to run in families. The body thinks that a harmless substance is a danger, so it produces reactions designed to repel and destroy the offender. If left untreated, an acute allergic reaction can result in death.

Some very severe allergic reactions require medical assistance. Hives and itchy eyes are not life threatening, but if the airways become restricted, anaphylaxis can ensue. This very serious symptom causes a person to pass out and stop breathing. An auto-injector needle filled with epinephrine can sometimes prevent anaphylaxis from occurring, but it is less effective if administered after a person loses consciousness. Epinephrine relaxes the throat and airways to allow breathing to resume.


Sometimes, an allergic reaction can be controlled through the use of antihistamines. Loratadine, cetirizine, and diphenhydramine are over-the-counter medications that block the body's histamine production and stop the body's overreaction. Antihistamines are produced in pill form and liquid suspensions. Some antihistamines can last up to 24 hours and do not cause drowsiness. People who suffer from allergies usually carry antihistamine pills with them at all times.

If someone is having an acute allergic reaction with an airway obstruction, then he needs immediate medical attention. Paramedics or doctors have the tools necessary to stop anaphylaxis from progressing. Pills or epinephrine needles generally will not help at this point, and over-the-counter drugs are not strong enough to combat this type of reaction.

People who suffer from severe allergies to certain substances should stay away from them, as the best way for one to prevent a reaction is to avoid the allergen completely. Antihistamines taken before allergen exposure can help reduce the risk of anaphylaxis, but there is no certainty with these medications. The only sure way to prevent reactions is to stay away from the allergy-causing substance.


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Post 2

My husband had a bad reaction to an antibiotic. He took it and later on that day, broke out in hives. He was completely miserable, and only Benadryl helped. He had these huge welts all over his back, especially. He was itching so, and nothing helped. I felt so sorry for him.

He was out of commission for a couple of days. He bought some oatmeal bath powder, which helped the itching, but the Benadryl made him groggy, so he wasn't driving or anything. The doctor put him on another antibiotic, obviously. The medication she had given him was new, and so she hadn't had any other patients who had bad reactions from it.

Post 1

I had an acute allergic reaction to a mosquito bite for the first time ever last year. It bit me on the middle finger of my left hand.

I knew it was itching, but then it started to swell and the tip started turning blue!

I went to the walk in clinic and the doctor couldn't believe a mosquito had done that to me. He thought sure it was a spider bite. He gave me a shot of Benadryl and some prednisone. I went home and crashed from the Benadryl and when I woke up, the swelling in my finger had gone down considerably, but it took a couple of days for it to get totally back to normal.

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