Grass pollen is an important cause of asthma and rhinoconjunctivitis in Europe and the United States. In the high Andes however, the role this pollen plays in respiratory allergies is unknown. In this study, we tested the prevalence of grass pollen sensitization in comparison to other aeroallergens on 433 asthmatic children living in Quito, Ecuador (the Andes mountain range, 2,800 m above sea level). The skin prick test technique was used. We found that the least sensitizing allergens of all were grass pollen (12.2%) and molds (7.4%) with p < 0.0001. A clear predominance of sensitization to the house dust mite Dermatophagoides pteronyssinus (77.8%) and Dermatophagoides farinae (76.9%), in comparison to the other aeroallergens tested, in terms of sensitization (p = 0.00000) and papule size (p < 0.0002), was observed. The most highly sensitized group consisted of asthmatics between 5 and 15 years of age (D. pteronyssinus 90.7%, D. farinae 87.5%, dog hair 37.4%, cat hair 43%, grass pollen 15.9% and molds 9.9%). In the total study group, males were only more sensitive than females to D. pteronyssinus (82.1% vs. 71.6%, p = 0.0009). We concluded that in the group of asthmatic children studied, grass pollen showed a low capacity of sensitization, even though it is widely found all over our city. The most sensitizing allergens were D. pteronyssinus and D. farinae, followed by cat and dog hair.