Severe allergies occur when the immune system reacts strongly to certain substances, known as allergens. Common allergens include pollen, dust mites, pet dander, and certain foods like peanuts or shellfish. Symptoms can range from hives and swelling to more serious reactions like anaphylaxis, which can be life-threatening. People with severe allergies often need to avoid specific allergens and may carry an epinephrine auto-injector for emergencies. Treatment options include antihistamines and allergy shots, which can help manage symptoms and reduce sensitivity to allergens over time. Awareness and preparedness are crucial for those affected.