This condition, which happens to everyone at some point, is also known as nasal congestion or nasal obstruction. While colds and flu are the best known causes of this, it can also be caused by other problems such as certain allergies (hay fever is the most typical), sinusitis or a reaction to medication. In each case the actual blocked nose is quite similar, although other symptoms may be different.
When you have a cold, your nose usually starts to feel blocked a day or two after you get the first symptoms of feeling shivery, sneezing and perhaps getting a headache. The blocked or runny nose (sometimes you can get both at once, which is the worst of all) usually starts about the same time as your cough, and may last for a week or more.
The reason cold symptoms vary is that there are several viruses that give you what we call the common cold. The most usual type is a rhinovirus. There are almost 100 viruses of this type affecting humans alone. The name comes from the Greek word for ‘nose’, and the viruses are given this name because they attack the nasal area and the throat area, which is closely connected to the nasal area (this is why if you have problems in this area you will be sent to an ear, nose and throat specialist. It is also part of the reason why, along with your blocked nose, you so often get a sore throat and a muffled or uncomfortable sensation in your ears as well).
The reason you get a blocked or a runny nose is the same reason you sneeze and get other cold-like symptoms: a rhinovirus works on the nasal area. Basically, it gets into the upper part of your respiratory tract (part of the passageways through which air goes in and out of your body, the entry point to which is your nose). It quickly attaches itself to surface receptors there, and like all viruses begins to replicate itself and to spread. In doing so, it infects cells in the respiratory tract area. The infection causes an inflammatory reaction as it activates chemokines and other cytokines (proteins which are activated by the body’s immune system when it’s attacked, eg by a virus). It is this that eventually results in all these irritating or even painful symptoms around the nose and throat regions – blocked nose, runny nose, sore throat and so on. It usually takes a week or more for the body’s immune system to fight off the virus and restore the functioning of the respiratory tract to normal.
One reason there is still no cure for the common cold is the huge numbers of viruses responsible. The rhinovirus with its 99 variations is just one of the viruses involved, so finding a treatment that deals with all these viruses – which like all viruses can adapt and change as well – is very difficult. For most people the body’s own immune system will deal with the virus and no further help is needed. Some people do like to take medication for colds, but this is usually aimed at masking the symptoms or relieving discomfort – no reliable way of speeding up the body’s immune response has yet been found, though conversely if you are generally in poor health or are under stress, it can take longer to fight the cold off. Overall, if you eat a good diet, take exercise and try to avoid undue stress, you are in the best possible position for your immune system to manage a cold virus by itself.
You can learn more about the symptoms, causes and treatment of the common cold here.