The classic example of allergy to inhaled substances is allergy to the pollen of the flowers of trees, grasses and weeds. These flowers are not usually colorful neither especially beautiful flowers as opposite as the flowers whose pollen is transferred from flower to flower by insects (in example by bees). These flowers are mainly small flowers and not so colorful that do not attract particular attention. These flowers spread their pollen by the wind.
In this category are very common allergens like pollen of certain trees (in example olive, cypress), pollen from weeds (like Artemisia) and various grasses.
An important characteristic of these allergies is the seasonality. The symptoms of these allergies closely parallel the flowering season of the eliciting plant.
It is also important to clarify that allergy to a specific pollen (for example to olive tree pollen) does not mean that there is an allergy to its fruit (in this example, to the olive itself).