For a small patch (under one square foot), a careful DIY clean may be sufficient. Wear an N95 mask and gloves. Mix a solution of one part white vinegar to four parts water, scrub the area, and allow it to dry completely. Do not use bleach, as it can sometimes exacerbate the problem on porous surfaces. Crucially, identify and fix the moisture source—this is often a small leak in the AC condensation line or a cold spot on an exterior wall.

However, given that the mold is in a child’s bedroom, the symptoms are present, and the growth is hidden (often indicating a larger issue within the wall), a professional inspection is strongly advised. They use moisture meters and thermal cameras to find the hidden source of moisture that you cannot see. A proper assessment includes air and surface sampling sent to an accredited microbiology lab to identify the species and spore count, which is the only way to confirm the health risk and verify the cleanup was successful. For health and safety, erring on the side of a professional evaluation is the most prudent course of action.