Coughing up small red particles may come from the glandular fossa of the tonsils.
Coughing up rice-sized particles is mostly from the glandular fossae on the surface of the tonsils. Each tonsil has 10-20 fossae, which are openings on the surface of the tonsil.
When people chew their food, they push food debris and oral bacteria into the glandular fossa. The body’s immunity is sometimes gained from the stimulation of these debris and bacteria. Food debris accumulates and rots over a long period of time and gives off an unpleasant odor. This is the reason why most of the foreign bodies are coughed up from the pharynx.
The presence of coughing up small red particles should be treated promptly by a medical professional.