Allergies are an exaggerated immune system reaction to foreign substances called allergens such as dust, molds, mites, foods, animal fur/pet dander, etc.

For people with allergies, these allergens induce the production of IgE antibodies that cause the release of histamine, a substance that causes a reaction in the blood vessels and smooth muscle tissue, allowing for the appearance of allergic symptoms that vary according to the part of the body involved.


This is a disorder that occurs following exposure to inhaled allergens (pollen, dust, etc.).

It manifests as nasal symptoms, for example post-nasal drip, sneezing, itching, nasal congestion, and runny nose (rhinorrhea) as well as eye problems (redness, itching, burning, and tearing). It is a clinical condition that adversely affects the quality of life, causes fatigue, headaches and irritability.


Urticaria, also known as hives is characterized by the sudden appearance of reddish-brown spots on the skin with a brighter spot in the center, that are very itchy and variable size and location, which generally persist for less than 24 hours. In the case of hives, histamine released at the skin level can be caused by allergens or drugs, foods, animal poisons, physical stimuli such as pressure, cold, and heat.

Harrison's Principles Of Internal Medicine.