While small surface mould can sometimes be cleaned with a vinegar or diluted bleach solution, the urgency here is due to three factors: the hidden nature of the growth, the presence of an infant with developing lungs, and the high probability the visible patch is just the tip of the iceberg. Spores will be circulating in the room’s air, which can exacerbate or trigger respiratory issues.

A professional inspection is critical. They will use moisture meters and borescopes to assess the wall’s internal condition and identify the true moisture source. Merely cleaning the visible mould without solving the underlying cause guarantees it will return. For a case like this, DIY is not recommended as improper cleaning can aerosolize a high concentration of spores, temporarily making the air quality worse.

Look for a company that provides a clear diagnostic report and a remediation plan based on IICRC standards. The process should include containment of the area, HEPA filtration to capture airborne spores during work, and post-remediation verification to confirm spore counts have returned to acceptable levels. This is the only way to be certain the environment is safe for your child.