An allergic reaction to allergy shots is quite common, but many of the symptoms of this condition are quite mild. Most patients who get allergy shots will experience mild versions of their regular allergy symptoms, including runny noses and watery eyes. Swelling on or around the injection site is also quite common. A severe allergic reaction to allergy shots, however, can sometimes result in anaphylactic shock. If the throat swells, it will cause breathing difficulties or possibly death.

Allergy shots are very similar to vaccines. They contain small amount of allergens, or substances to which a person may be allergic. When these allergens are injected into the body, the immune system produces antibodies that help prevent allergy symptoms. Technically, nearly everyone has an allergic reaction to allergy shots.

Many times, symptoms of an allergic reaction to allergy shots consist of typical allergy symptoms. For example, if a person experiences watery eyes and nasal congestion when exposed to pollen, he will often experience these symptoms when getting allergy shots. These symptoms are typically very mild, however, and they will usually last no more than a couple of days. An oral antihistamine can help reduce these symptoms.

Local skin reactions after an allergy shot are not uncommon. Swelling and redness around the injection site, for example, are quite common during an allergic reaction to allergy shots. These symptoms can begin either immediately after allergy shots or several hours later. Like the other symptoms, these are typically minor and will often go away quickly.

A more severe reaction to allergy shots can include anaphylactic shock. This can cause a drop in blood pressure. If this occurs, a person may feel dizzy or lightheaded and possibly faint. A rapid heartbeat may also occur during a severe allergic reaction to allergy shots.

Severe swelling of the face and surrounding areas can also occur during anaphylactic shock. A person's eyes, lips, or tongue may swell, for instance. Swelling of the throat can constrict the airways, causing breathing difficulties.

Treating an allergic reaction to allergy shots is very important. Without the proper treatment, a person could die. Patients who get allergy shots are usually required to stay in an examination room or a waiting room for up to an hour afterward. This gives doctors an opportunity to observe them for any adverse reactions. If this occurs, an epinephrine, or adrenaline, injection may be necessary to reverse these side effects.