A 3-year-old has increasing serosanguineous drainage from one nares. What foreign body is the most likely cause?

The scenario describes a 3-year-old child with increasing serosanguineous drainage from one nostril, which suggests that there is likely a foreign object causing irritation or injury to the nasal passage. In this context, a magnet is a plausible and concerning option due to its potential complications.

When a magnet is lodged in the nasal cavity, it can cause tissue ischemia and necrosis, leading to serosanguineous drainage as the blood vessels and surrounding tissues become inflamed or damaged. Magnets can attract each other if multiple magnets are present, exacerbating the injury and increasing the likelihood of serious complications.

While other foreign bodies like button batteries and fishing weights can also cause significant harm, the symptoms may not specifically present as serosanguineous drainage in the same way that magnets do. Dried beans may cause nasal obstruction and irritation but are less likely to lead to bleeding and drainage. Therefore, the characteristics of the drainage and the type of foreign body indicate that a magnet is the most likely cause in this scenario.