Echinacea is an herb, or flowering plant, that grows throughout the United States and Canada. Practitioners of alternative medicine frequently use it as an herbal remedy to treat the common cold, according to WebMD. In addition, echinacea can treat vaginal yeast infections, states Drugs.com.
Herbal supplements, teas and liquid extracts can include all parts of the echinacea plant, including the stem, leaves, flowers and roots, according to WebMD. The most common side effect when taking echinacea is an upset stomach. Other side effects include a rash, anaphylaxis or worsening asthma, if the individual already suffers from asthma, according to WebMD.