The polyethylene construction of these disposable syringes usually makes them rather chemically resistant. There is, however, a risk of the contents of the syringes leaching plasticizers from the syringe material. Non-disposable glass syringes may be preferred where this is a problem. Glass syringes may also be preferred where a very high degree of precision is important (. quantitative chemical analysis ), because their engineering tolerances are lower and the plungers move more smoothly. In these applications, the transfer of pathogens is usually not an issue.
Stinging nettles hurt so much when you touch them you will have a very strong sensation of burning and itching. Nettle plant of herb genus Urtica, chemist shows how tiny hairs inject venom to produce pain. If you brush or rub the hairs on the plant, called trichomes, their fragile silica tips break off to release a cocktail of chemicals into the base of the hair, which cause the hard sting and burning until showing blisters on the skin. Those hollow stinging hairs which act like hypodermic needles, injecting histamine and other chemicals that produce the hard stinging sensation and burning are distributed by the stems and leaves of the plant. If you also whip your skin with nettles, the blisters will appear reddish. Nettles are used in some extreme German videos but curiously you can also see them in recipes.