With recent weather conditions many homes are beginning to get mould. A common practice in cleaning mould is to douse it with bleach, which appears to be effective.
In actual fact bleach makes things worse. Because of it's acidity, it makes the fungi go deeper into the surface it is growing on and it actually feeds it. The reason why bleach makes the wall look clean is because it leeches the colour out the mould but doesn't actually kill it. Mould has melanin like our skin, making it darker the more it is exposed to the sun. Bleach strips the melanin out of the fungi, so bleach is stripping the colour from the mould. This is why six weeks or so later the mould comes back when it regains its colour.
Clove oil will kill the mould though it will leave a residue and is expensive. Methylated spirits or plain white vinegar are the best solutions for killing mould. They actually penetrate into the fungi and make it explode. The solution is 70 percent white vinegar with water or 80 percent methylated spirits mixed with water. Mix your solution in a bucket and wipe down the infected area with your solution. Rinse your cloth in another bucket of clean water to avoid further contamination. Most mould is invisible so it's best to clean the surrounding area as well. After applying the solution, the fungi is killed but the melanin will still be there leaving the stain. To remove this, you can use a clean microfiber cloth and scrub until it is gone. It will also be helpful to establish the source of the mould and remove this if possible.
Mould left untreated can cause health issues such as respiratory problems, infections and skin irritations and even changes in mood getting depressed or grumpy. These are associated with long term exposure to high quantities.
It's best to get expert help to remove the mould if you have more than 1 square meter of mould in your home.
Reference: https://www.abc.net.au/local/stories/2011/02/25/3149028.htm