There are several indicators that you may have mould in your property. It could be a sign of mould if you experience unexplained allergic reactions such as sneezing, coughing, or a runny nose. Additionally, if you notice that your asthma symptoms are worsening or becoming more frequent, this may indicate mould in your property. Visible mould growth on walls, ceilings, or other surfaces clearly indicates a problem. Finally, persistent dampness or water stains on your property can also signal a mould issue.