Table 1.

Complementary and alternative medicine therapies for the common cold

INTERVENTION	EVIDENCE FOR PREVENTION (LEVEL*)	EVIDENCE FOR TREATMENT (LEVEL*)
Echinacea purpurea	No evidence found in 2 RCTs (level IIa)8,9	Evidence found in 5 of 6 RCTs (level IIa)10–15
Zinc lozenges	No trials evaluate prevention	Evidence found in 5 of 9 RCTs (level IIa)16–24
Vitamin C	Evidence found in meta-analysis of 30 RCTs; more benefit in children and in adults under stress (level I)25	No evidence found in meta-analysis of 11 RCTs (level I)25
Ginseng	Inconsistent; evidence found in 2 of 4 RCTs (level IIb)26–29	No trials evaluate treatment
Garlic (allicin)	Evidence found in 1 RCT (level IIb)30	No trials evaluate treatment
Probiotics	No evidence found in 4 of 6 RCTs (level IIa)31–36	No trials evaluate treatment

RCT—randomized controlled trial.

^*Levels of evidence indicated are taken from the Oxford Centre for Evidence-Based Medicine.³⁷