You may or may not notice that you are allergic to something the first time you are exposed to it. Sometimes, your body can have an immune response to an allergen, but you won't feel sick. But the next time you are exposed to this same allergen, your body will recognize it and react to it, and this time you'll know, because you will feel the symptoms. This is called an allergic reaction. The symptoms you experience will depend on what type of allergen you are exposed to, where you were exposed on your body and how allergic you are.
Allergic reactions vary from person to person and can be very mild or very serious.
Some people have much more severe seasonal allergies with runny nose, congestion, watery eyes and more, whereas others may just sneeze once in a while. A very severe type of allergic reaction, known as anaphylaxis, can lead to shock and ultimately death if not treated immediately. During this severe reaction, your body produces chemicals that can cause great difficulty breathing, muscle contractions, stomach cramps, and low blood pressure, which can lead to shock. Your healthcare provider could give you either a skin test or a blood test to determine what is causing your allergies. Not everyone needs these tests, but if your allergies are bothering you and you don't know what is causing them, talk to them about taking these tests to find out.