Like its botanical relative true indigo ( Indigofera tinctoria), wild indigo has historically been used as a source of a deep blue dye. It was also used medicinally: the natives of North America used it as a topical treatment for non-healing wounds and infections of the mouth and throat. The root is the part used.

What Is Wild Indigo Used for Today?

Currently, wild indigo is primarily used as part of a standardized four-herb combination said to improve immune function. This combination contains, besides wild indigo, Echinacea purpurea root, Echinacea pallida root, and white cedar ( Thuja occididentalis). This combination is hypothesized to have immune-stimulating properties.

In a well-designed double-blind study of 263 people with recent onset of the common cold, use of this combination significantly improved cold symptoms as compared to placebo.1 Recovery occurred approximately 3 days earlier among people taking the herbal mixture as compared to those taking the placebo.

Benefits for the common cold were also seen in other double-blind, placebo-controlled studies involving a total of about 250 people.2,7

The same combination therapy has also shown promise for augmenting the effects of antibiotics in people with bacterial infections.2 For example, in one study, 53 people experiencing an acute exacerbation of chronic bronchitis were given either antibiotics plus placebo or the same antibiotics plus this herbal combination.3 The results showed that participants receiving the herbal mixture recovered significantly more quickly than those given placebo.

Proponents of this combination therapy claim that it works by “balancing” or “strengthening” the immune system.2, 4-6 However, while there is evidence that this herbal mixture affects the immune function, the current state of scientific knowledge is generally inadequate to determine whether any such effects are good, bad, or indifferent. See the article on immune support for more information on this widely misunderstood topic.

Dosage

Combination therapies containing wild indigo, echinacea, and white cedar should be taken according to label instructions.

Safety Issues

Wild indigo has not undergone comprehensive safety testing. However, in clinical studies, use of the standardized combination therapy has not been associated with any serious harmful effects. Safety in young children, pregnant or nursing women, or people with severe liver or kidney disease has not been established.