Introductory Remarks
The use of alternative and herbal therapies in the U.S.A. has grown enormously over the past few years.  This has created some controversy among health care providers, with many professionals holding opposing views on their safety, efficacy, and clinical applications.  Some of the points which must be considered include

Efficacy -- Does the therapy work?  This may be based upon extensive scientific and/or clinical data.  The absence of such data would seriously question the appropriate use of a product or preparation.  The efficacy, or at least the basis for potential efficacy, may be established by

Scientific data

In vitro data -- data generated from isolated preparations, either cellular or tissue in nature, that reflects some mechanism of action and/or pharmacodynamic effect.

In vivo animal data -- data generated from testing in some animal model.  This most often provides pharmacodyanamic data and may or may not include a mechanistic basis.

Clinical data -- data generated from human trials examining the claims and efficacy of the prepartion.

Side Effect, Toxicity, and Drug Interaction Profiles -- Ideally, each of the above tests should also examine the side effects and toxicity and potential drug interactions of the preparations.  This, however, is rarely done.  Many herbals, while potentially useful, may also produce bothersome, dangerous, and even life-threatening side effects and toxicities.  This may reflect the nature of many products marketed that are whole plant or plant part extracts that contain, in addition to the specific, beneficial constituent, numerous other constituents that cause adverse reactions.

Standardisation of Dosage and Product -- The third valid concern of many professionals is the lack of standardisation of doses and constituent content in the various products.  For example, some products may contain only 1-5% activie ingredients while others may contain as much as 20-25%.  The former may be "subtherapeutic" while the latter is toxic.

Allergic Rhinitis

Nettle -- Urtica dioica has been suggested as a treatment for allergic rhinitis and asthma.  One component, scopoletin, has shown anti-inflammatory actions in laboratory studies.  However, there are no clinical data to support efficacy or use in these disorders.  It does possess diuretic actions and use may cause electrolyte imbalance and contact dermatitis.

Pill-bearing Spurge -- Euphorbia hirta has been used through the ages for many disorders, including ashtma.  Rodent studies indicate that extracts possess anti-inflammatory properties.  However there are no human studies to support any efficacy in the treatment of asthma.  Side effects include cholinergic overload, contact dermatitis, and gastro-intestinal upset.  The FDA has ruled that extracts are neither safe nor effective for treating asthma.

Heachache and Migraine

Feverfew -- This herbal is derived from a member of the chrysanthemum family, bachelor's button (Chrysanthemum parthenium, also known as Tanacetum parthenium or Pyrethrum parthenium).  Numerous constituents are found in extracts, with the primary component of benefit identified as parthenolide, a sesquiterpene lactone.  Mechanistically, this has been shown to inhibit serotonin release.  Other extracts have been shown to inhibit activation of inflammatory cells and to inhibit the synthesis of leukotrienes and prostaglandins.  Suggested doses range from 25-200 µg daily for prevention to 500 µg for treatment of migraine.  In randomised, double-blinded studies, patients suffering from migraine had significantly fewer attacks and significantly less nausea and vomiting associated with migraines when administered feverfew vs. placebo.  There were no differences in severity of pain when attacks occurred.  Reported side effects include hypersensitivity reactions, mouth ulcerations (with crude drugs) and a withdrawal syndrome of joint and muscle stiffness and pain.  Although human data does support a potential efficacy with feverfew in the prevention of migraine, problems with standardisation of product suggests that caution should be used in taking products indiscrimantly.

Glucosamine is a natural component of mucopolysaccharides, mucoproteins, and chitin.  Biochemically, it is one of the components used in the synthesis of synovial fluid and therefore is present in joints as part of these larger structures.  Extensive use and research in veterinary medicine has indicated a significant improvement in hip mobility in dogs with arthritis.  Mechanistically, this is believed to represent an increase in the synovial components that help cushion joints and thus delay the progress of the arthritis.  Early clinical trials in humans have also indicated some benefit in administration of glucosamine.  NOTE, however that many researchers believe that the compound must be co-administered with ascorbate and manganese that provide anti-oxidant and co-factor functions respectively in the synthesis of the mucopolysaccharides (Therefore recommendations should include all three components).  Additionally, veterinary use has indicated that administration early in the disease progression has much better results than use late in the disease when substantial joint damage (structurally) has already occurred.  Side effects associated with glucosamine in humans include constipation, diarrhœa, drowsiness, GI pain, headache, and rash.  There is evidence to support benefit of glucosamine for the treatment of arthritis, especially early in the disease, but additional human studies need to be conducted to fully document efficacy, safety, and potential toxicity.

Cayenne --  Extracts of various pepper plants (Capsicum frutescens, C. annum, C. baccatum, C. chinensis, and C. pubescens), belonging to the Solanaceae family, serve as the source of capsaicinoid oleoresin, an oily extract that contains as its primary constituent capsaicin.  (Note that the Piper species, the source of black (P. nigrum) and white pepper is botanically separate from these peppers.)  These plants are also very rich in various vitamins including C (ascorbic acid).  Interesting, when cooked the peppers retain approximate 1/3 of their ascorbate but when they are dried, all vitamin C is lost.  Topical administration of capsaicin will cause intense irritation without vesiculation (blistering), which reflects a lack of activity on the vasculature.  Individuals report initial pain with subsequent analgesic and anti-inflammatory actions.  The initial "heat" is due to stimulation of local afferent pain fibres and initial release of the pain mediator subtance P.  The mechanism of analgesic action is a depletion of this substance P from the neurone, especially from the dorsal root ganglia of the spinal cord.    It has been theorised that the methoxyphenol portion of the molecule may also decrease LOX and COX activity.  Capsaicin is available in topical cream (0.025%, 0.075%, and 0.25%), gel (0.025%), and lotion (0.025%, 0.075%) and in "pepper spray" or mace (5% and 10%).  It is used topically for pain associated with arthritis, diabetic neuropathy, post-herpetic neuralgia, and post-surgical (mastectomy and amputation) pain.  Side effects include blepharospasm, eye irritation, nasal irritation (most often from rubbing these areas with inadequately washed hands following application), and transient skin irritation.  Capsaicin may decrease the efficacy of centrally-acting antihypertensives (methyldopa, clonidine).  The mechanism of this interaction is not know.  Application is recommended t.i.d. to q.i.d.  This regimen will allow sustained analgesia, but patients should be counselled that the onset of analgesia is relatively slow.