Fungal spores are one of the main groups of allergens. They are present in our environment all year long. The concentration of the spores in July and August is 100-1000 higher than pollens. In contrast with the pollens there is a correlation between the spore count and higher risk of medication use, nocturnal asthma attacks, and hospitalization rates. We have presented the clinical classification of fungi, and characterized main indoor and outdoor allergens. The fungi play also an important role in the sick building syndrome. Fungal allergens are not only aeroallergens, they may also get into our body with food. They may also develop contact reactions. Antibiotic allergy is regarded as one of the classic allergic reactions caused by fungi. The id reactions are caused by the fungi from far infection focuses.