Anaphylaxis is a severe, potentially life-threatening allergic reaction. Symptoms typically emerge within minutes of exposure to an allergen and peak within the first two hours, though in some cases they can extend up to 4-6 hours.

Key signs and symptoms include:
* Skin Reactions: Hives (urticaria), itching, rash, redness, swelling (face, lips, tongue, throat).
* Respiratory System: Difficulty breathing, coughing, wheezing, hoarseness, a sensation of throat constriction, runny nose, sneezing.
* Cardiovascular System: Low blood pressure (hypotension), increased or decreased heart rate, dizziness, fainting.
* Digestive System: Nausea, vomiting, abdominal pain, cramps, diarrhea, urinary incontinence.
* Neurological Symptoms: Dizziness, fainting, fatigue, weakness.

In anaphylaxis, at least two organ systems are typically affected. Although skin manifestations are the most common, approximately 10% of cases may not show any skin symptoms. Involvement of the respiratory and cardiovascular systems indicates a life-threatening condition. Isolated symptoms like rapid onset 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. Symptoms can vary in the same person at different times and with different triggers.