It starts with a small black spot on the wall or between tiles in the bathroom: small mouldy spots like these can quickly become a big problem in cold weather. This is because mould grows several centimetres a day when the conditions are good. First things first: What can you do about it? Even if the spots are still small, they should not be ignored but intead removed as quickly as possible. “You can remove smaller areas of up to half a square meter yourself, provided you don’t have an allergy or a weakened immune system,” says Guido Fischer from the Baden-Württemberg State Health Authority. I…