Background: Since year 3000 BC, pollenology (science that studies allergens) was already known. In the year 49 BC, Herodotus recognized the first case of hay fever, Jacob Constant (17th century) described the first case of allergic rhinitis and related it to "something" (allergens) that roses emitted. Charles Backley (1873) proved the ability of the skin to determine allergic reactions to allergens. Today, it is well-known that allergens are able to react with environmental exposure, plants and pollens.
Objective: To know the most common allergens in allergic patients who are admitted into a tertiary care hospital.
Material and methods: 3,172 electronic expedients of registered allergic patients were examined. Only 356 fulfilled the inclusion criteria. Five groups of allergens were studied: group 1 (pollens), 2 (fungus), 3 (inhaled allergens), 4 (food) and 5 (other allergens), the value of seric IgE was registered too.
Results: The main allergens that were found are: 156 (43.8%) Amaranthus palmeri, 163 (45.5%) Candida albicans, 262 (73.6%) dust mite, 33 (9.3%) chicken and 4 (1.2%) apple/pineapple. The main diseases were: 254 (71.3%) allergic rhinitis, 52 (14.6%) asthma-rhinitis, 39 (11%) asthma and 63 (17.6%) others, the value of seric IgE was minimum of 1 and maximum of 9,620 Ul/dL.
Conclusions: Allergens affecting patients are not different of what is reported in world-wide literature; however, it is of great significance to know this and take it as a guideline to achieve clinical improvement with the use of an appropriate immunotherapy.