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  • Writer's pictureDr. Koralla Raja Meghanadh

4 Stages of Sinusitis - Acute, Chronic, Subacute, Acute on Chronic

Updated: May 18

Stages of sinusitis - acute, subacute, chronic, acute on chronic

How Sinusitis starts?

For a person to get sinusitis, they must have a few underlying problems like -

  1. allergies

  2. anomalies in the structures like sinus opening and drain paths of sinuses that are responsible for draining infected fluids

  3. low immunity towards bacteria by birth

When people with the above conditions are infected with common viral infections like the common cold, swelling in the nose structures can occur, resulting in the stagnation of the fluids in the sinuses. These stagnated fluids will be responsible for hosting bacteria that can infect the sinus walls causing sinusitis. The chances of getting sinusitis will decrease drastically if the common cold is treated with proper medication under a doctor's guidance.

Read our article "causes of a sinusitis infection," where we clearly describe how each of the three factors mentioned above can contribute to sinusitis.

Stages of Sinusitis

There are four stages of sinusitis and they are

  1. Acute

  2. Subacute

  3. Chronic

  4. Acute on chronic

Sinusitis is a condition that develops in stages. It begins with an acute stage, progresses to a subacute stage, and eventually becomes chronic. The chronic stage is the longest-lasting and typically has milder symptoms that persist over time. However, if a person's immunity weakens or develops another infection, the chronic stage may progress to a more severe stage with additional sinusitis symptoms. This stage is known as acute on chronic sinusitis.

Here is a table giving you a gist about the stages of sinus infection.


When does it start?


About Symptoms


5 days after a nasal infection

around 10 days (day 5 to day 15 from the start of nasal infection)

Symptoms get severe compared to those in the first 5 days of nasal infection.


After the acute sinusitis stage

around 30 days (day 15 to day 45 from the start of nasal infection)

Symptoms get less severe, and the number of symptoms can decrease


After the subacute sinusitis stage

indefinite time (from 45 days after the start of nasal infection)

Very few or negligible symptoms with very little severity

Acute on Chronic

Whenever the immunity of a person with chronic sinusitis takes a hit

Stays till immunity is down

Very severe symptoms that can disrupt daily life

Acute sinusitis

As mentioned earlier, most sinus infections start with common viral infections like the common cold. These viral infections usually subside within 5 to 7 days. In this period, the stagnation can begin due to swelling of nasal structures, and bacteria grow in these fluids. The bacteria can affect the skin lining of the sinuses resulting in sinusitis.

Due to sinusitis, common cold symptoms worsen. These sinus infection symptoms can be -

  1. Nose block

  2. Running nose

  3. Headache

  4. Fever

  5. Loss of smell

  6. Congestion or redness of the eyes

  7. Phlegm coming from the back of the nose into the throat

  8. Recurrent attacks of cough

Unlike the common cold, these symptoms can hinder the patient's daily life due to their severity. The worsening of these symptoms indicates that symptoms are turning from viral to bacterial, i.e., infection is turning into acute bacterial sinusitis or acute sinusitis.

So, in zero to five days, the symptoms were for the flu, and in six to fifteen days, the symptoms belonged to acute sinusitis. If the individual takes proper treatment religiously within fifteen days, this sinusitis is more likely to get cured, and all the symptoms should disappear. If the acute sinusitis treatment is partial, the intensity of the symptoms will decrease.

To know more about acute sinusitis, check out this blog.

Subacute sinusitis

Subacute sinusitis is a stage that can occur when acute sinusitis is only partially treated or left untreated. The subacute sinusitis will continue for about one month, i.e., from the 15th day of the infection to the 45th day.

Although the decrease in symptoms will give a false notion that the disease has subsided, the chance of progressing to chronic gets higher with this stage. With the start of this stage onwards, doctors may want to do a minor sinus surgery as a part of the treatment, and the number of tests done as a part of diagnosis compared to acute also increases.

It is common for doctors and online articles to group the acute and subacute stages of sinusitis. However, it is essential to recognize significant differences in the approaches used for diagnosis and treatment between these stages. Therefore, distinguishing between acute and subacute sinus infection can be crucial for effectively managing and resolving the condition.

To know more about subacute sinusitis.

Chronic sinusitis

After 30 days of subacute sinusitis, i.e., after 45 days of infection, it turns into chronic sinusitis. In chronic sinusitis, the number of symptoms decreases to one or two with lesser severity and is not at all troubling the patient.

Here an equilibrium between the bacteria and immunity is reached. The symptoms are only reduced, deceiving the patient. A compromise between infection and immunity is achieved, but the disease does not reduce internally.

As the symptoms have subsided, patients have the wrong notion that the sinusitis is in control and come to terms with the existing symptoms. But, internally, the infection has not decreased, and there is a potential risk of it spreading to the voice box, ears, and lungs.

You can read about the chronic sinusitis here.

Acute on Chronic sinusitis

Whenever a chronic sinusitis patient goes into colder weather, the nasal mucosa slightly swells, adding to the other sinusitis factors. Already partially blocked openings or drainage pathways will be blocked more or get blocked. When the total blockage happens, the bacteria grow more, and the symptoms will increase, similar to acute sinusitis. This stage is called "acute on chronic" sinusitis. Both the number and severity of the symptoms will also increase in acute on chronic sinusitis. The patient can experience new symptoms.

This stage can happen whenever a chronic patient moves to a cold or dusty environment or if they get another viral infection.

Many attribute acute on chronic sinusitis to food like ice creams or cool drinks, but it depends mainly on the environment or viral infections and not on foods.

To know more about acute on chronic sinusitis, click the link below.

Written by


What are the stages of a sinus infection?

Sinusitis has 4 stages they are acute, subacute, chronic, and "acute on chronic" are four stages of sinusitis.

What is the difference between sinusitis and acute sinusitis?

The main difference between sinusitis and acute sinusitis is that acute sinusitis is just one stage of sinusitis. Acute sinusitis is the first stage and typically lasts for the first 15 days. Acute means very severe, so in the acute stage, the number and severity of the symptoms are more compared to future stages. Due to lack of proper treatment, acute progresses to subacute sinusitis, which will last for one month, followed by chronic sinusitis. In both subacute and chronic, the number and severity of symptoms will decrease gradually. But, if a chronic patient gets into cold weather or gets another viral infection, this chronic can move into a stage called "acute on chronic" sinusitis, where the symptoms will increase, like in acute or even more.

Knowing which stage of sinusitis we are in is essential, as the diagnosis and treatment will depend on it.

What is the longest sinus infection?

Chronic sinusitis is the longest sinus infection. Dr. K. R. Meghanadh, our author, has seen patients with chronic sinusitis for as long as 40 years. It is not uncommon to see people suffering from chronic sinusitis for decades. Whenever a sinus infection lasts for more than 45 days, it turns into chronic. Chronic sinusitis is caused when acute and subacute sinusitis is left untreated or partially treated. Even though chronic sinusitis persists for several months or even years, we can cure it with proper treatment.

Which sinusitis is most common?

Acute bacterial sinusitis is the most common. In most cases, it doesn't proceed to further stages and resolves itself. It occurs after viral rhinitis or the common cold.

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