Anaphylaxis is a severe allergic reaction, and its symptoms can vary from person to person and depending on allergen exposure. The most common signs and symptoms are generally observed in the following systems:

* Skin Reactions: Hives (urticaria), itching, rash, redness, and widespread swelling (angioedema). Skin symptoms may not be present in some cases (approximately 10%).
* Respiratory System: Difficulty breathing (dyspnea), wheezing (stridor/wheezing), coughing, runny nose, itchy nose, sneezing, swelling of the tongue and/or throat (risk of airway obstruction).
* Cardiovascular System: Low blood pressure (hypotension), increased (tachycardia) or decreased (bradycardia) pulse rate, dizziness, fainting.
* Gastrointestinal System: Nausea, vomiting, abdominal pain, cramps, and diarrhea.
* Other Symptoms: Fatigue, weakness, and rarely urinary incontinence.

Anaphylaxis signs and symptoms typically appear within the first two hours after contact with an allergen. This period can be as short as a few minutes or, in some cases, extend up to 4-6 hours. For diagnosis, involvement of at least two organ/system is generally required. Involvement of the respiratory and cardiovascular systems poses a life-threatening risk.

Rapidly developing isolated symptoms such as hoarseness, a feeling of throat constriction, or low blood pressure after exposure to a known allergen (e.g., bee sting or medication use) can also indicate anaphylaxis. Different symptoms may occur in the same person at different times and with different triggers.