Reported side effects of echinacea include dry mouth, stomach discomfort, joint pain and headaches, according to WebMD. Individuals taking echinacea may also experience an unpleasant taste in their mouths and feel disoriented when taking the supplement. Individuals with auto-immune disorders such as lupus and rheumatoid arthritis should not take echinacea, as it may aggravate their conditions.
Additional reactions and side effects that can occur when taking echinacea include heartburn, constipation and tongue numbness, explains Mayo Clinic. When taken orally or applied topically for up to eight weeks, echinacea is likely safe. However, when taken on a long-term basis, the supplement may lower white blood cell counts. Individuals who suffer from ragweed or marigold allergies should also avoid taking echinacea.
Individuals commonly use echinacea to minimize symptoms that accompany upper respiratory infections such as the common cold, notes the University of Maryland Medical Center. However, research results vary on the actual effectiveness of the herb. For example, as of 2015, 14 clinical trials have shown that supplementing with echinacea reduces the duration of cold symptoms by one to four days, while other studies found that the herb had no effect. Preparations of echinacea can also vary in strength, so it is always best for anyone considering taking the supplement to consult with a medical professional for dosage recommendations.