A water damaged ceiling is usually caused by a leaky roof. Water is a substance that always goes down the path where there is least resistance. The first sign of leaky roof water damage is usually a yellowish discoloration of the paint on the ceiling. The other way you can get a water damaged ceiling is by having an upstairs bathroom leaking water. A pipe bursting or heavy rain fall can aggravate a leak and cause severe damage. The results of the damage are extremely visible, because water will drip, and ends up on the top part of the ceiling material, whether it is drywall, wood or plaster.
The damage caused to the ceiling and walls by the water is downright ugly and unsightly. The ceiling becomes damp from the pool of water that begins to form over time. The material becomes weaker and starts to lose its integrity. This issue can be costly and repairs to drywall have to be done carefully. This type of problem can be repaired relatively quickly and at low cost. The major problem with the water damage is that mold can form after just a few days. The mold can be the source of health problems and should be removed immediately.
The Dangers of Mold
Mold is very dangerous because it grows rapidly in moist and dark places, making ceiling leaks extremely susceptible to mold exposure. If drywall or plaster is damp for even a few days mold can grow and spread. When the ceiling is damp or wet you must act quickly to dry it out immediately. A fan must be placed in the direction of the affected area and left for several days, to ensure it dries out completely. Mold damage can be very expensive, so acting quickly is in your best interest. The health hazards related to mold are many. It is imperative that you take this very seriously. You must also keep in mind that paint chips may contain lead. Lead in paint, especially in older homes, can be unhealthy. When in doubt, it is better to consult with a professional specializing in lead paint removal.

Stopping the Leak and Drying the Ceiling
When the problem is detected, you must proceed to stop the leak. The leak can come from a variety of sources such as the roof, a broken pipe or an upper floor leak from the kitchen or bathroom. If you rent you must inform the landlord and your upstairs neighbor if necessary. It defeats the purpose to repair the damaged ceiling if the leak is not stopped. This type of leak can also cause mold that must be addressed as well. The repairs will only mask the problem a short period of time and may cause greater damage and mold. Leaks, no matter how small, can be a warning that there is a more serious problem that must be addressed.
You must assess the leak and dry it up as fast as possible. A bucket can catch the dripping water leak. Towels can be used to soak use the excess standing water above and below the leak. You can also use a mop to dry the area, and a vacuum to suck up the water. A fan can be used to dry up the water efficiently. Many times the leak is more severe than you first thought. If the ceiling is bulging, it usually is a sign that it is full of water. You may need to poke a hole in the ceiling with a screw driver, knife or an ice pick. This will give relief to the pressure and give the water an exit. Make sure to place a bucket below the hole and watch for the water that may come gushing down. Always use caution with these kinds of issues, because you do not want to be exposed to any harmful fumes or toxins.