The symptoms of the common cold can be vague and may overlap with those of other, more severe illnesses. The likelihood of a specific illness being present depends on the age of the person experiencing the symptoms. For illnesses that may follow on from the common cold, see Complications.

• Influenza ranges from asymptomatic carriage to severe, life-threatening infection. Milder symptoms of influenza are frequently misdiagnosed as the common cold. If symptoms of muscular pain (myalgia) or fever are prominent, suspect influenza. See the CKS topic on Influenza - seasonal.
• Streptococcal pharyngitis may cause a sore throat that is mistaken as the common cold. Usually pain is more severe if infection with Streptococcus pyogenes is responsible, and cough, sneeze, and nasal congestion are absent. See the CKS topic on Sore throat - acute.
• Allergic rhinitis can present with nasal symptoms similar to those of the common cold. See the CKS topic on Allergic rhinitis.
• Infectious mononucleosis (glandular fever) is prevalent in young adults and adolescents. It is a chronic infection characterized by prolonged fever, a severe sore throat, fatigue, and swollen lymph nodes.
• Meningitis. Signs and symptoms that make a diagnosis of meningitis more likely include:
• Purpuric rash that does not fade when a glass is pressed against it.
• In infants and babies — a high fever; loss of consciousness; blank, staring expression; vomiting and loss of appetite; high-pitched screaming or whimpering; floppiness, with a dislike of being held; and/or a tense or bulging fontanelle.
• In older children and adults — fever, vomiting, stiff neck, photophobia, severe headache, muscular pains, fits, stomach cramps (caused by septicaemia), and/or confusion.
• Pertussis (whooping cough) may cause prodromal symptoms similar to those of the common cold, but it should be easily diagnosed once the characteristic cough develops.
• A foreign body should be considered if a child has a persistent, unilateral nasal discharge in the absence of other symptoms.