Constant coughing teenager

The short version: a constant cough in a teenager is most likely from asthma, post-nasal drip from allergies, or reflux — and the evidence for each is thin on long-term safety of the drugs used to treat them.

The retrieved evidence is a grab bag of case reports and guidelines, not a systematic review of a teenager with constant cough. One 2025 case report describes a 16-year-old boy with asthma and chronic cough who turned out to have nontuberculous mycobacteria lung infection plus severe reflux [1]. That is a single case, not a population. The German Respiratory Society guideline [2] and the Russian review [9] both define chronic cough as lasting more than 8 weeks and list the same top causes: asthma, upper airway cough syndrome (post-nasal drip from allergies or sinusitis), and gastroesophageal reflux. A Chinese review adds cough-variant asthma and eosinophilic bronchitis as common causes [4]. A Japanese study found that air pollution, especially ozone-related oxidants, increased coughing in children with asthma who were not on controller medication [5]. A follow-up study of children hospitalized with pneumonia found they were about 3 times more likely to have persistent cough years later [6].

What is missing from this retrieval is any long-term safety data on the drugs used for these conditions. The montelukast pilot study [3] was small (14 patients), funded by no one named, and only two weeks long — it says nothing about the neuropsychiatric side effects montelukast carries. The oral immunotherapy study [7] was tiny (10 active, 8 placebo) and funded by no one named; it found cough did not improve significantly. The broccoli seed glucoraphanin report [8] is three COVID-19 cases, not a treatment for chronic cough in a teenager.

The real question for a parent is not "what causes chronic cough" but "what is the safest way to find out." The standard approach — try an inhaled corticosteroid for asthma, a nasal steroid spray for allergies, or a proton-pump inhibitor for reflux — is based on consensus, not on trials that compared these drugs to placebo in teenagers and measured all-cause harm. The German guideline [2] is a consensus document, not a trial. The Chinese review [4] says about 80% of patients respond to specific therapy, but that is in adults, not teenagers, and "respond" means symptom improvement, not cure.

My call: the most likely causes are asthma, allergic rhinitis with post-nasal drip, or reflux, in that order. But the evidence for the drugs used to treat them in teenagers is weak on long-term safety. Start with environmental changes — removing allergens from the bedroom, a trial of a saline nasal rinse, keeping a symptom diary — before reaching for a prescription. If you try a drug, know what side effects to watch for. Confidence: moderate that these are the common causes, low that the standard drug treatments have been adequately tested in this age group.