It depends on the case; there is no single guideline.
Effect by goal · level of evidence
Inflammation and immunity
no clear effectLowstudy (A)
Review proposing that electrical contact with the earth would reduce inflammation and improve healing. The evidence is scarce, from small studies and often from the advocates/sellers of products themselves: effect not reliably demonstrated.
Inflammation and immunity — no clear effect (Low, study). Review proposing that electrical contact with the earth would reduce inflammation and improve healing. The evidence is scant, comes from small studies, and often from the advocates/sellers of products themselves: effect not reliably demonstrated. 25848315
Information, not medical advice. Prescription drugs require a doctor.
Information, not medical advice. Scientific evidence reflects the quality of the studies.