First, isolate the area. Seal the bathroom door with plastic sheeting and tape. Wear an N95 mask, gloves, and protective eyewear. Never use a dry brush or sandpaper, as this aerosolizes the spores. Instead, lightly mist the mold with water to suppress spores, then scrub with a dedicated brush and a cleaning solution. A mix of white vinegar or a diluted bleach solution (1 part bleach to 10 parts water) can be effective, but ensure the room is extremely well-ventilated during and for hours after using bleach.

The critical step is that if the mold has penetrated behind the sealant or into the grout/ wall, surface cleaning is insufficient. You must completely remove and replace the silicone sealant. Any remaining moisture or mold residue underneath will cause it to return rapidly. After removal, the area must be thoroughly dried and treated before applying new, high-quality mold-resistant sealant.

Given the extent you’ve described and the persistent respiratory symptoms in your household, this situation likely requires professional assessment. DIY efforts on significant growth can inadvertently expose your family to higher concentrations of spores. A certified inspector can use moisture meters to check for hidden dampness in the walls and take air or surface samples for lab analysis to confirm the mold type and concentration, which is crucial for understanding the health risk and ensuring the remediation is fully effective.