The popularity of herbal medicines and dietary supplements is increasing all over the world due to the many side-effects assigned to synthetic drugs. Herbal remedies should be considered as safe, with no side-effects, but unfortunately, even if they are labelled as natural, large numbers of adulterants, not only with toxic heavy metals but also with undeclared synthetic substances, have been detected up to date. In this review, the most frequent instances of adulteration of herbal medicines and dietary supplements acting as sexual enhancers and slimming products are thoroughly discussed. The great success of synthetic phosphodiesterase type-5 (PDE-5) inhibitory drugs like sildenafil, vardenafil and tadalafil, used for the treatment of erectile dysfunction has made them, as well as their Unapproved analogues, popular as adulterants in herbal dietary supplements. The second group among blockbuster products are herbal preparations for slimming purpose, as obesity and gaining weight are major problems worldwide. Here, sibutramine hydrochloride monohydrate, an anti-obesity drug which inhibits serotonergic and noradrenergic reuptake, seems to be the most common adulterant. Together with large numbers of its analogues, thyroid hormones, anorexigens, diuretics, stimulants, and laxative agents are also detected in most of tested diet supplements. (C) 2016 Elsevier Ltd. All rights reserved.