Herbal teas are often consumed for their physical or medicinal effects, especially for their stimulant, relaxant or sedative properties. The medicinal effects of certain herbs are discussed under herbalism . The medicinal benefits of specific herbs are often anecdotal or controversial, and in the United States and elsewhere, makers of herbal teas are not allowed to make unsubstantiated claims about the medicinal effects of their products.

While most herbal teas are safe for regular consumption, some herbs have toxic or allergenic effects. Among the greatest causes of concern are:

1.Comfrey, which contains alkaloids that can cause permanent liver damage with chronic use.

2.Lobelia, which contains toxins similar in effect to nicotine. Although Lobelia is known for its astounding blood cleansing qualities.

3.Chamomile and Pineapple weed (another Matricaria species), are closely related to ragweed and can cause violent allergic reactions in hay fever sufferers, up to and including anaphylactic shock and death.

Herbal teas can also have different effects from person to person, and this is further compounded by the problem of potential misidentification. The deadly foxglove, for example, can be mistaken for the much more benign (but still relatively hepatotoxic) comfrey.

The UK currently does not require natural products such as herbs to have any evidence concerning their efficacy, but does treat them technically as food stuff and require that they are safe for consumption.