Mildew is hard to ignore but thankfully easy to get rid of once you find the source of it. Mildew can show up anywhere there is moisture present -- even if it's just the drippings off a raincoat. Once mildew grows, it can give off a musty smell that transfers to fabrics around the area. In a wardrobe, the small space, lack of circulation and amount of clothing can accentuate the smell. Not only that, but if not removed, the mildew can spread and begin to wreck the items it touches--like books, sheets, pillows and that expensive jacket hanging next to the raincoat! Once you locate mildew in a cupboard or wardrobe, try to figure out the source of the moisture. Is it just the raincoat or is there a leaky ceiling? Make sure you take care of the root of the problem so that the mildew does not regrow. Then, you can work on getting rid of the mildew and its smell.
Empty out the wardrobe and inspect each item for signs of mould or mildew. Put aside any clothing that has visible mould or a strong smell on it for the cleaners or washer. Throw out mouldy books or papers. Also clear out shoes and inspect both inside and outside for mould.
Once the wardrobe or cupboard is empty, plug in the dehumidifier and set it just inside the door. This will take the remaining moisture out of the air. If you do not have a dehumidifier, try positing fans in the doorway to dry out the wardrobe. Circulation will help dissipate the smell as well.
Mix a solution of equal parts hot water and white vinegar. Wipe down the walls and any shelving units completely. Dry afterwards with a clean towel. If there are any drawers in the wardrobe or cupboard, take them out and clean with the vinegar solution, but do not put back in yet.
If you have a carpeted cupboard or walk-in wardrobe, use carpet cleaner to sanitise the floor. Otherwise, use a fresh vinegar/water solution to clean the floor.
Leave the doors open for two to three days to dry out the cupboard or wardrobe. Keep humidifier on and make sure the room has circulation.
Remember, the point is to get rid of the mildew smell and not to cover it up with air fresheners or perfumes.
If you have drawers or other removable shelving in the cupboard or wardrobe, take them out to clean. If possible, leave in a sunny area (outside) to dry.
Leave the doors open a bit to circulate the air or chose a door with venting.