Anaphylactic shock is a particularly severe form of allergic reaction, which may be fatal if not rapidly and properly cared for. The allergens which may bring on anaphylactic shock are varied, and in some cases even a trace amount of the allergen is enough to trigger full anaphylactic shock. Because of its extremely quick action, anaphylactic shock is responsible for many deaths in the United States and worldwide. It is estimated that more than 400 people die each year in the United States from anaphylactic shock brought on by insect stings, and more than 125 people die each year as a result of food allergies.

The symptoms of anaphylactic shock are varied, but may often include such things as a constriction of the airway, light-headedness and fainting, swelling of the neck and face, itching and low blood pressure. A constricted airway, caused by a constriction of the bronchiole walls, is the most common cause of death in cases of anaphylactic shock. This will often occur within minutes of contact with the responsible allergen, and unless emergency assistance is on hand or very nearby, there is little one can do to restore air flow.

Those who have been diagnosed in the past with severe allergic reactions may carry on them some form of easily administrable epinephrine (adrenaline). The most common brand of autoinjectable epinephrine is EpiPen, designed to be self-administrable. It is highly recommended that anyone with a high risk of anaphylactic shock carry some form of epinephrine on their person at all times. In the United States, these devices require a prescription. While occasionally additional doses of epinephrine may be required to fully counter the affects of the allergen, care must be taken that the secondary dose is not injected too soon, as this can cause an increased heartbeat which may carry its own health risks.

Some of the most severe cases of anaphylactic shock come from allergens which are very common in the modern environment, such as peanuts and soybeans. Great care must be taken by those with high sensitivity to these allergens to avoid them. In an attempt to reduce the deaths caused by anaphylactic shock, the United States requires food companies to disclose whether their products are manufactured in a facility that also processes common allergens, as even trace levels may be enough to trigger anaphylactic shock. Other allergens commonly responsible for anaphylactic shock include: the stings of bees, wasps, and some ants; dairy; fish and shellfish; nuts; latex; and some drugs such as penicillin.