An allergic reaction is an immune system response to a particular substance or food that the body senses as harmful – even though it shouldn’t be. Most allergic symptoms are fairly mild and may include hives, watery eyes, sinus congestion, diarrhea, facial flushing, nausea, itching and inflammation. However, severe allergic reactions can be extremely dangerous and even life-threatening – especially anaphylactic shock but also asthma attacks and heart palpitations. Some of the most common allergy triggers include substances such as pollen, dust mites and pet dander; foods such as shellfish and peanuts; materials like latex; and insect bites including bee stings and mosquito bites. Because allergy symptoms may worsen with continued exposure to certain allergens, it’s important to talk to your physician about even mild itchiness, rashes and other symptoms that you suspect may be the result of an allergy. They can diagnose your allergic triggers via skin prick tests, intradermal tests, patch tests and blood tests.