We are reporting a study evaluating the crossover of antigens reacting in Platelia Aspergillus (PA) enzyme-linked immunosorbent assay (ELISA) from faeces to vessels during mucositis as a possible cause of false-positivity of this test. In our series of 102 episodes of different grades of mucositis, we found strong reactivity of faeces in the PA ELISA test irrespective of the grade of mucositis, the percentage of oral food intake or the presence of total parenteral nutrition. However, none of the patients included in the study were positive in the serum (when the criterion of two samples with cut-off index of positivity [IP] > 0.5 was used).