Substances that are normally harmless to the human body but cause various reactions in allergic individuals are called allergens. The reactions that occur when exposed to these allergens are called allergic reactions.
Allergic reactions can manifest with various symptoms such as redness, swelling, itching, shortness of breath, sneezing, runny nose, watery eyes, diarrhea, nausea, and vomiting, starting from the face and affecting a specific part or the entirety of the body.
The body parts affected by an allergy can vary depending on the type of allergen and its entry route into the body. For example:
Allergens inhaled through the respiratory tract, such as pollen, typically cause symptoms in the nose, eyes, sinuses, and throat.
Food allergies often lead to stomach or intestinal problems and can cause skin reactions like hives (urticaria).
Some allergic reactions can also affect multiple parts of the body simultaneously.
Generally, the most common allergy symptoms are:
Redness, swelling, and itching on the body
Sneezing
Runny nose
Watery eyes
Shortness of breath
Diarrhea
Nausea and vomiting