context: Ever find yourself sneezing, wiping your nose, nursing a headache, or trying to hide a skin rash when everyone around you seems fine? You might be allergic to something. But what is it? You often can solve the mystery yourself if you know where to look. Each is an important clue. Signs of an allergic reaction, from mild to severe, include: Chest tightness Diarrhea Feeling faint, confused, weak, or about to pass out Hives -- small reddish bumps that look like bug bites suddenly appear on your skin Itchy, dry rash Odd taste in your mouth Nausea or vomiting Red skin, often around your eyes Runny nose or sneezing Stomach pain Swollen lips, tongue, or throat Trouble swallowing Anaphylaxis is the most severe reaction you can have. It's life-threatening and often food-related. Insect stings, certain meds, and latex can cause it, too. It can affect several areas of the body at once, like your skin, nose, mouth, and gut. You might have a hard time breathing. Your blood pressure may drop, making you feel weak or confused. You could even lose consciousness. If you have any of these symptoms, call 911 and get to an emergency center right away. If you've had such a reaction before, you're more likely to have one again. Allergy symptoms happen when your immune system overreacts to something that doesn't bother most other people. Whatever's causing this is called an allergen. For instance, allergies might affect you only at certain times of year, like in the spring, when pollen abounds. Or they can flare up when you make contact with something -- like when you eat, dust, or touch a certain plant or animal. Whatever the trigger, your system thinks it needs to fight it. Allergens enter your body in different ways. If you can figure out how, you'll be that much closer to finding your culprit. By injection. This could be medicines given by needle, or venom from insect bites or stings. Mouth. Common food allergens include peanuts, fish, and shellfish. Nose and lungs. They can be small specks or have spores that float in the air, like pollen, animal dander, dust, mold, grass, or weeds. Through your skin. These can include poison ivy, oak, or sumac. Chemicals in cosmetics, dyes, and latex can also spark a reaction. What did you do today? What did you eat, and how much? Did you take any meds? Where did you go? How did you feel? The answers to these questions can help you find your allergy trigger. When you track your symptoms and what was going on when you had them, it helps pinpoint the cause. It also can help you figure out what makes it worse. This info will help your doctor decide how to treat your allergy, too. Be sure to note if other people in your family have allergies, and what they are. Online journals are handy ways to log your symptoms and ID your triggers. They range from forms that you fill in to calendars that let you track your allergy attacks at a glance. Digital journals often are geared toward particular types of allergies. For example, do your symptoms show up in your eyes, nose, and chest? You'll want to track allergens you breathe in. Do you have a reaction in your digestive system, your stomach, or your mouth? Try a food allergy diary. Apps can help track your triggers, info about your surroundings, and even weather forecasts, on the go. Have you had symptoms as long as you can remember, or did they just appear? Did you move to a different part of the country? Tried a new medication? Tried a new food? Some other common allergy triggers to think about: Cockroaches Dust mites. These are tiny bugs that live in pillows, carpets, mattresses, and upholstery. Certain foods and drugs. Indoor molds. They thrive on moisture, such as dampness, humidity, and water leaks in your environment. Latex. Outdoor mold and pollens. These ebb and flow with the seasons, which can catch you off guard. Pollen in the spring and ragweed in the fall are common culprits. Pets. You can be allergic to your pet's skin, saliva, or urine. People with other allergies are more likely to be sensitive to furry friends, too, especially cats. Put down your magnifying glass and call for help. The Asthma and Allergy Foundation of America's free info line, 1-800-727-8462, is open weekdays from 10 a.m. to 3 p.m. ET. This line isn't for emergencies. Call 911 if you're having a serious reaction. Once you've gathered the facts, it's time to see your doctor or a specialist. A board-certified allergist can help you figure out if your ideas are correct and how serious your allergy is. He might: Discuss your symptoms Ask about your medical history Use blood or skin tests to verify your allergy Prescribe over-the-counter or prescription meds or allergy shots to relieve your symptoms Tell you how to change your environment or personal habits so you'll feel better