Reactions to allergic triggers may be mild or may rapidly progress to respiratory or cardiovascular collapse and death.
Sometimes a reaction evolves over hours.
The allergic triggers are usually food (especially nuts and shellfish, but also peppers), medications, or insect stings.
The symptoms typically involve the skin (hives, flushing, itching) and may also include the respiratory system (wheezing with respiratory failure) and the cardiovascular system (low blood pressure and shock).
When an anaphylactic reaction hits, a flood of chemicals, primarily histamine, are dumped into the bloodstream.
Produced by specialized blood cells that respond to injury, infection, or allergic triggers, histamine
is normally released locally in tissues as part of the body’s defense mechanism.
But during anaphylaxis this response goes haywire.
When large amounts of histamine pour into the circulatory system, blood vessels lose their elastic tone and get leaky.
Floppy, leaky blood vessels fail to squeeze down when you are upright, so blood pools in your extremities instead of flowing back to the heart. Cardiac output falls and blood pressure drops, leading to shock and possible fainting. In severe reactions, patients may experience shock even while lying down.
Patients can experience tingling lips, which can be part of an allergic response, and dangerously low blood pressure.
It’s a diagnosis made purely on clinical grounds; there is no time to wait for confirmatory blood tests, since it can be fatal if not treated promptly. Although there are other causes of shock, if there is any reasonable suspicion of anaphylaxis, it’s always better to treat first and ask questions later.
Elevate the patient’s legs to increase blood return to the heart and brain and inject a dose of adrenaline into the thigh muscle. Adrenaline quickly restores tone to the blood vessels and ramps up the strength and speed of cardiac action. Start an IV and run it through stat to restore the volume of liquid circulating through the arteries. Give Oxygen to maximize the amount of oxygen the blood can deliver to the tissues.