Rare, but high doses (over 1,000mg) can sometimes cause dizziness or nausea. For the best effect, it shouldn't be taken for more than one to two weeks at a time.

Therapeutic uses: to prevent and fight infections, especially colds, flu, coughs and sore throats. Can be helpful for chronic fatigue syndrome, allergic conditions such as asthma and hay fever, shingles, herpes and mouth ulcers, or applied topically for eczema, boils or acne.