For a small, isolated patch (under one square meter), you can clean it yourself safely. Wear an N95 mask, gloves, and eye protection. Scrub the area with a solution of detergent and water; avoid bleach as it doesn’t prevent regrowth and can damage porous surfaces. After cleaning, dry the area thoroughly with a fan. The critical step is addressing the moisture source. This is often condensation from the AC unit or a small leak. Ensure your AC is set to a temperature that minimizes the drastic temperature difference between the cold interior and the hot exterior wall, and check that the condensate drain line is not blocked.

Given the location on an exterior wall and the recurring symptoms, a professional inspection is highly recommended. They can use a moisture meter to identify the exact source of dampness hidden within the wall cavity, which DIY cleaning cannot address. In the UAE, proper remediation often involves corrective measures for the building envelope itself. If the mold returns after cleaning, or if the affected area is large, a certified mold inspector can identify the species and the full extent of the problem to ensure it is resolved correctly.