Winter Colds

This is not a knock on the Rio Grande Valley of Texas, as it probably happens elsewhere, but what does anyone know about what we call "The Texas Crud"? Many of my Winter Texan friends develop symptoms similar to a cold; red eyes, runny nose, coughs, that can last five or six weeks. Some have it all winter. Self-treatments include over the counter meds as well as prescription antibiotics from Mexico. None seem to work reliably or sometimes at all. Does anyone have definitive diagnosis and a regimen that works? Please don't suggest going elsewhere as a cure since we love our Winter Texan experience otherwise.