1.  Reasonable entails a method of operation consistent with scientific knowledge.  Nearly always the quack claims that there is a pathway; for example, the polarity of molecules was affected by magnets in a way that increasing the rate of healing for a broken bone or injured joints.  However, magnets do not affect in a useful way polar molecules.  This is because compared to the energies of electrons and the molecular distances involved in a chemical reaction, the magnetic force is insufficient to have an effect. It is for this reason that magnets are not used in chemistry lab to modify chemical reactions.  The modus operandi touted by the quack is not reasonable:  it is nothing more than a sales gimmick.

2.   For a drug to be effective it must be administered in medicinal amounts.  For example 10 mgs of codeine relieves pain, but 1mg doesn’t.  The same is true of all drugs; there is an optimal effective dose.  In herbal preparations generally the individual substances are not present in sufficient quantities to have a curative effect.  Moreover, with few exceptions, unrelated compounds do not have an additive effect.  When a chemical found in a plant or fungus has a potentially useful effect, the scientist then isolates and concentrates that chemical (not the whole cocktail of compounds) so as to be able to administer it in a medicinal dose. 

3.  Thousands of treatments have been tried by tribal care givers; however, nearly always their use remains local.  Successful treatments, like opium for pain, become widely used.  Moreover, in the search for curative chemicals medical science has tested many of these herbs.  If a chemical therein could have a possible a curative effect, it is then concentrated into a medicinal dose and then tested.      

4.  Any treatment worth its salt will be tested and the results submitted to a medical journal.  If magnet on the wrist cured liver dysfunction, then the manufacturer of that product ought to advance its marketing by having a study done and then published in an important medical journal.  Being published does not prove the case:  there are trade publications for alternative treatments and the editorial review of the submitted works are scanty at best and fall well below scientific standards.

5.  True believers are as much a proof of angels dancing on the head of pins as that of the curative property of the magnet.  And just as there are scientists who profess to believe in a young earth, so too are there physicians and researchers whose beliefs are equally questionable.  These experts who violate their science are the rare exception. 

6.  Reproducibility is part of the gold standard.  A result that stands in conflict to a large body of evidence is always more like to be in error. 

Consider the following example (from http://quackwatch.org/04ConsumerEducation/QA/magnet.html)by Stephen Barrett, MD. 

The main basis for the claims is a double-blind test study, conducted at Baylor College of Medicine in Houston, which compared the effects of magnets and sham magnets on knee pain. The study involved 50 adult patients with pain related to having been infected with the polio virus when they were children. A static magnetic device or a placebo device was applied to the patient's skin for 45 minutes. The patients were asked to rate how much pain they experienced when a "trigger point was touched." The researchers reported that the 29 patients exposed to the magnetic device achieved lower pain scores than did the 21 who were exposed to the placebo device [3} Although this study is cited by nearly everyone selling magnets, it provides no legitimate basis for concluding that magnets offer any health-related benefit:

• Although the groups were said to be selected randomly, the ratio of women to men in the experimental group was twice that of the control group. If women happen to be more responsive to placebos than men, a surplus of women in the "treatment" group would tend to improve that group's score.
• The age of the placebo group was four years higher than that of the control group. If advanced age makes a person more difficult to treat, the "treatment" group would again have a scoring advantage.
• The investigators did not measure the exact pressure exerted by the blunt object at the trigger point before and after the study.
• Even if the above considerations have no significance, the study should not be extrapolated to suggest that other types of pain can be relieved by magnets.
• There was just one brief exposure and no systematic follow-up of patients. Thus there was no way to tell whether any improvement would be more than temporary.
• The authors themselves acknowledge that the study was a "pilot study." Pilot studies are done to determine whether it makes sense to invest in a larger more definitive study. They never provide a legitimate basis for marketing any product as effective against any symptom or health problem.

Two better-designed, longer-lasting pain studies have been negative:

• Researchers at the New York College of Podiatric Medicine have reported negative results in a study of patients with heel pain. Over a 4-week period, 19 patients wore a molded insole containing a magnetic foil, while 15 patients wore the same type of insole with no magnetic foil. In both groups, 60% reported improvement, which suggests that the magnetic foil conveyed no benefit [4].
• More recently, researchers at the VA Medical Center in Prescott, Arizona conducted a randomized, double-blind, placebo-controlled, crossover study involving 20 patients with chronic back pain. Each patient was exposed to real and sham bipolar permanent magnets during alternate weeks, for 6 hours per day, 3 days per week for a week, with a 1-week period between the treatment weeks. No difference in pain or mobility was found between the treatment and sham-treatment periods [5].