Whooping cough symptoms can appear from three to 21 days after exposure to the infection. During the first two weeks the symptoms may resemble those of colds, asthma or allergies, so these conditions will need to be ruled out by a physician. Whooping cough infection generally has three stages that unfold over six to 10 weeks or longer. Symptoms are generally milder for teens and adults. Symptoms tend to be worse for children and those who never have been vaccinated for whooping cough.

The first stage (catarrhal) begins within days or weeks after infection and lasts from several days to two weeks. An infected person is most contagious during the first stage of the infection. Symptoms during this phase resemble those of a common cold or allergy and include:

• Sneezing
• Runny nose
• Nasal congestion
• Mild, dry coughing
• Watery eyes
• Mild fever

In babies, the following symptoms may also be present:

• Bluish or pale complexion
• Bulging or watery eyes
• Arms and legs flailing in distress
• Tendency to stick out tongue or push chest forward

During the second stage (paroxysmal), early symptoms fade, but are replaced by waves of violent, wet coughing fits that bring up mucus. These episodes are so intense that breathing during them may be nearly impossible. When the cough finally subsides, the person is likely to gasp for breath. As air rushes into the body through narrowed airways, a “whooping” sound may follow.

Some of the symptoms of the second stage include:

• Wet coughing spells of a minute or longer, 15 to 24 times in a 24–hour period
  
  
• Attacks that occur more often at night
  
  
• Patient turning red from effort, or blue from cyanosis (lack of oxygen)
  
  
• Vomiting and severe exhaustion after coughing spells
  
  
• Tiny, red spots (petechiae) on the skin of the upper body due to blood–vessel ruptures
  
  
• Small areas of bleeding in the whites of the eyes
  
  
• Ribs bruised or broken during intense coughing

The paroxysmal stage is the most serious stage of whooping cough, and it lasts for one to six weeks or longer. Between coughing spells, a person may appear healthy. In addition, infants may not make the “whooping” noise usually associated with the second stage. Infants with whooping cough have an increased risk for pneumonia.

During the third stage (convalescent), the coughing often becomes louder, but the patient improves and becomes stronger. Coughing spells continue to flare up sporadically, especially if the patient has a cold or other respiratory illness. The third stage lasts two weeks or longer.