All herbs are not equal: some contain poisons, some don't; some of
 the poisons are not so bad, some can kill you dead. I divide herbs into
 four categories for ease in remembering how (and how much) to use. Some  herbs
 nourish us, some tonify; some bring us up or ease us down and some are frighteningly strong.

 Nourishing herbs are the safest of all herbs. They contain few or no
 alkaloids, glycosides, resins, or essential oils (poisons).
 Nourishing herbs are eaten as foods, cooked into soups, dried and
 infused, or, occasionally, made into vinegars.. They provide high-level
 nutrients, including vitamins, minerals, trace minerals, proteins,
 phytoestrogens and phytosterols, starches, simple and complex sugars, bioflavonoids,
 carotenes, and essential fatty acids (EFAs).

 Nourishing herbs in water bases (infusions, soups, vinegars) may
 generally be taken in any quantity for any period of time. Side- effects --
 even from excessive use -- are quite rare. Nourishing herbs are rarely
 used as tinctures (in alcohol), but when they are, their effects may be
 quite different.

 It is generally considered safe to use nourishing herbs in water
 bases with prescription drugs. They may also be taken even if you are
 using  tonifying, stimulating/ sedating, or potentially poisonous herbs.

 Tonifying herbs are generally considered safe when used in
 moderation.
 They may contain alkaloids or glycosides or essential oils, but
 rarely in quantities sufficient to harm us.

 Tonifying herbs act slowly in the body and have a cumulative, rather
 than immediate, effect. They are most beneficial when used for extended
 periods of time. Tonifying herbs may be used regularly (but usually not
 daily) for decades if desired.

 Tonifying herbs are prepared in water and alcohol bases: tinctures
 and wines, as well as infusions, vinegars, and soups.

 The more bitter the tonic tastes, the less you need to take of it.
 The more bland the tonic tastes, the more you can use of it.

 Side effects from overuse and misuse of tonics is uncommon but quite
 possible. The dividing line between what is tonifying and what is
 stimulating differs from person to person. Ginseng is tonifying to
 my sweetheart, but stimulating to me. Even herbal authorities disagree
 on which herbs are tonifying and which stimulating.

 Take care to counter any tendency to overuse tonifying herbs or you
 may experience unwanted side effects.

 It is generally considered safe to use tonifying herbs in water
 bases if  you are taking prescription drugs. You may also use tonifying herbs
 while  using nourishing, stimulating/ sedating, and even potentially
 poisonous herbs. Tonifying herbs in alcohol bases are considered safe to use
 with nourishing herbs, but may produce unexpected results if combined
 with drugs or strong herbs.

 Stimulating/ sedating herbs frequently contain essential oils,
 alkaloids,
 glycosides, or resins. Because these substances cause strong
 physical
 reactions, stimulating/ sedating herbs are known from their rapid
 and pronounced effects, some of which may be unwanted.

 Stimulating/ sedating herbs are most often prepared as tinctures
 (and wines), vinegars, teas, and infusions. Many stimulating/ sedating
 herbs are used as seasonings in cooking as well. Despite my cookbook's
 injunction to  use only a little, I long ago learned that more aromatic herbs in my
 soups gave a "livelier" result.

 Because long-term use of stimulating/ sedating herbs can lead to
 dependency, dose and duration of use must be carefully watched. A
 moderate to large dose, taken infrequently will produce better results than a
 small dose taken over a longer period.

 Side effects from the use of stimulating/ sedating herbs in water
 bases are not common but possible. Side effects from use in alcohol bases are
 frequent. Whenever stimulating/ sedating herbs are used regularly,
 health is compromised.

 It is not safe to take prescription drugs with stimulating/ sedating
 herbs, but they may be taken even if you are using nourishing and/or
 tonifying herbs.

 Potentially poisonous herbs always contain alkaloids, glycosides,
 resins, or essential oils. And they contain large quantities of those
 poisons, or in very potent forms.

 Potentially poisonous plants can cause death directly, through the
 actions of their poisons on their targets (such as cardiac glycosides which
 stop the heart) or indirectly, by causing the liver and/or the kidneys to
 fail (as they attempt to cope with and clear the poison from the system).

 Potentially poisonous herbs are usually extracted into alcohol
 (tinctures) and used in minute doses (1-3 drops). For safety sake use
 potentially poisonous herbs as infrequently as possible and for the shortest
 possible time.

 Powdering and encapsulating increases the risk of side effects from
 any herb, but when we take stimulating/ sedating and potentially
 poisonous herbs in capsuled, the side effects can be deadly.
 Homeopathic pharmacy uses many potentially poisonous plants, but in
 such dilute doses that death is impossible. Side effects can occur, even
 with homeopathically tiny doses, however.

 Potentially poisonous herbs activate intense effort on the part of
 the body and spirit and may cause nausea, visual disturbances, digestive
 woes, and allergic reactions even when used correctly.

 Always be extremely cautious when using potentially poisonous herbs.
 Consult with at least three other knowledgeable herbalists who have
 used the plant in question before proceeding.

 In general it is not considered safe to take potentially poisonous
 herbs which taking prescription drugs, other potentially poisonous herbs,
 or stimulating/ sedating herbs. It is generally safe to use potentially
 poisonous herbs while using nourishing and tonifying herbs.

author unknown