Summarize this article in one sentence.
Most of the time, your reaction will begin within a few minutes of eating the first bite of food. However, sometimes, it can show up hours later. One symptom is a tingly tongue after eating shellfish. Other symptoms include wheezing, coughing, throat tightness, hoarseness, and trouble breathing. You also might break out into hives, have itchy, swollen eyes, or have swelling in your throat. Another symptom is stomach problems, such as diarrhea or vomiting. Finally, it can make you feel dizzy or lightheaded. If you have severe allergies, you may have what's called an anaphylactic reaction, which is just a fancy way of saying a severe, life-threatening allergic reaction. If you know your allergies are bad, you may need to inject your epinephrine when you first have a symptom. Otherwise, you will need to inject under one of these conditions: You have symptoms involving your nose, mouth, skin, or stomach, as well as you are having difficulty breathing or you're feeling light-headed and dizzy (low blood pressure). You think you were exposed to shellfish, and you have two of these symptoms: skin problems/swelling lips, stomach issues, low blood pressure (dizziness), or trouble with breathing. You know you were exposed, and you start to experience low blood pressure (dizziness, feeling light-headed, weakness). If you think you need to inject epinephrine, get out your pen. If you don't think you can do it yourself, try to talk someone else through it. Each pen is a little different, so make sure you read your instructions well ahead of needing to use a pen. Basically, though, you twist off the outer holder to reveal the auto-injector. You pull off the first cap, often blue, grey, or orange. On some pens, it's marked "1." You may see a red tip. Do NOT put your finger in front of the tip. Pull off the other cap. Place the needle end (the red tip on some pens) of the injector on the outer part of your thigh near the top and in the middle. Make sure it is going into the muscle. You can do it through clothing. Press down until you feel the needle enter your skin. Hold it for 10 seconds, then pull it out. Look at the tip to make sure the needle is extended. If it's not, you need to try again. You will likely see leftover fluid in the pen. That is fine, and as long as the needle extended, you received the proper dose. It can be helpful to show close friends and family how to use your epinephrine injector when you are in a non-emergency situation. That way, they can help should the need arise. Though the epinephrine can save your life, it does not solve the problem of the allergic reaction. You still need to go to the emergency room. It is best to call 9-1-1 right away.

Summary:
Recognize the early warning signs. Pay attention to the onset of symptoms. Inject with epinephrine. Go the emergency room.