An allergic reaction usually occurs within minutes of contact with an allergen, but can also occur several hours after exposure. A reaction can include any of the following symptoms, and a person may have one or more of these symptoms, regardless of the allergen:

• Cutaneous system (skin): hives, swelling, itching, feeling hot, redness, rash
• Respiratory system (breathing): coughing, wheezing, shortness of breath, chest pain or tightness, throat tightness, hoarse voice, nasal congestion or hay fever-like symptoms (runny or itchy nose, watery eyes, sneezing), difficulty swallowing
• Gastrointestinal system (belly): nausea (feeling sick), pain or cramps, vomiting, diarrhea
• Cardiovascular system (heart): pale or bluish complexion, weak pulse, fainting, dizziness/vertigo, shock
• Other: anxiety, feeling of “imminent danger”, headaches, uterine cramps, metallic taste in the mouth

The most dangerous symptoms of an allergic reaction are:

• Difficulty breathing caused by swelling of the airways (including a severe asthma attack in people with asthma);
• A drop in blood pressure causing dizziness, malaise, feeling weak or fainting.
• Both of these symptoms can lead to death if left untreated.

Do not forget :

• Do not ignore the first symptoms.
• Always take a potential reaction seriously and act quickly.
• Not all reactions are alike; a person's symptoms may vary from episode to episode.
• Anaphylaxis can occur even in the absence of skin symptoms such as hives.
• A child may describe their symptoms differently than an adult: for example, they might say, "It tickles in my throat" or "I have an itchy tongue."