Maybe, but not by much. Recent study results indicate that some echinacea supplements may shorten the duration of a cold by about half a day and may slightly reduce symptom severity. But these results were too minor to be deemed significant.
In the past, some studies have found echinacea to be helpful while other studies have found no benefit. Part of the problem is that echinacea products can contain different concentrations of the herb, and the echinacea extracts used in these products can come from the flowers, stems or roots of three different echinacea plant species. This makes it difficult to compare study results.
Echinacea generally doesn't cause problems for most people, but some people taking the herb have reported side effects such as stomach upset or diarrhea. Echinacea also has the potential to interact with other medications you might be taking, so talk with your doctor before using echinacea supplements.