Anaphylaxis

• Skin changes. The skin may show flushing and hives or swelling, or it may become itchy.
• Cardiovascular system signs. These signs may include rapid heart rate, low blood pressure, shock, arrhythmias (changes in heart rhythm) and loss of consciousness.
• Gastrointestinal system signs. These signs include distension (abnormal pressure and expansion of the abdomen), vomiting, diarrhea, nausea, pain or cramps.
• Respiratory system signs. These signs include swelling of the airway, wheezing and difficulty breathing. The tongue could swell and block the airway.
• Other symptoms. Other symptoms may include sweating, a sense of impending doom and a metallic taste in the mouth.

Common allergens that may cause anaphylaxis include:

• Food 
• Stinging insects
• Medicines, especially antibiotics
• Injections like vaccines and allergy shots

Rarely, symptoms of anaphylaxis can occur without an allergen being involved or identified. This type of reaction is called an anaphylactoid reaction. Features of anaphylactoid reactions include:

• Exercise
• Use of nonsteroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen
• Use of direct mast cell releasers like contrast media or chemotherapeutic agents
• Idiopathic cases (no cause is found)

More than 70 percent of children who have anaphylaxis will have respiratory system symptoms, and over 80 percent will have hives or swelling of the deep tissue of the skin, lips or tongue. Your child might experience an anaphylactic reaction in as little as a few seconds after being exposed to the allergen, or the reaction may build over a few hours. The more serious reactions tend to happen quickly. Reactions may come in two phases: an early phase and one that may be delayed for six hours. When the reaction occurs more than two hours after exposure, it tends to be less severe.

Some children may experience anaphylaxis after exercise. Their skin may itch with or without hives, and they may have low blood pressure and difficulty breathing. Eating food such as celery, wheat or shellfish a few hours before exercising may be a trigger for this rare problem.

Diagnosis of Anaphylaxis

Anaphylaxis occurs when your child’s immune system creates an antibody called immunoglobulin E (IgE). This antibody is associated in exaggerated immune responses—hypersensitivity or "classic" allergy. If there is an allergic reaction, the immune system’s interaction of the IgE antibody and the allergen causes the allergic symptoms.

Allergy testing, done with the skin prick test after a detailed medical history, can find the substances (allergens) that may have caused your child to make this antibody (IgE) and have this kind of a reaction.