This is a direct investigation of the biomedical effects of algae and house dust mites in patients with clinical house dust allergy and matched controls. Seasonal variation in clinical symptoms and objective changes in nasal patency will be evaluated serially every three weeks for two years. Other objective indices (specific IgE and leucocyte histamine release) will also be monitored. House dust samples will also be collected every three weeks during the heating seasons of the study. Quantitative mite and algae data will be derived from these samples. Temporal fluctuations of these organisms will be compared to clinical and laboratory changes in the patients and physical conditions of the indoor environments. Additional clinical and cross allergenicity studies with autogenous mite and algal extracts prepared from individual dust samples will be conducted.