Echinacea works to increase the activity of the immune system by stimulating white blood cells, which attack the viruses and bacteria that lead to illness or infection. This also makes it very beneficial for people with AIDS since their immune systems are weakened. Echinacea is also every effective in treating respiratory ailments like colds. Some research has found Echinacea to be effective as an antiviral or antifungal, which also helps it fight infection.