Nettle agents

Combined with other agents, they are of some value in piles and diarrhea. The fresh juice will give relief from insect and nettle stings. 

It is clear that histamine is not the only mediator of an allergic reaction, but it is unquestionable that this alkaloid plays a very important role in the reaction. That is why an antihistaminic agent is active against the expansion of capillary vessels and the contraction of bronchi. Clinically it is used for nettle rash and allergic inflammation of the nose. On the other hand, an antihistaminic agent cannot suppress bronchial spasms or the secretion of gastric juice. These phenomena are explained in that a different compound exhibits the same biological activity as histamine, and because of the different receptors of histamine. 

Formic acid methanoic acid H —C —OH O II Stinging agents of certain ants and nettles used in food preservation... 

Formic acid and acetic acid are the two most important carboxylic acids. Formic acid is a source of irritation in the bites of ants and other insects or in the scratch of nettles. A liquid with a sharp, irritating odor, formic acid is used in manufacturing esters, salts, and plastics. Acetic acid is present in a concentration of about 5% in vinegar and is responsible for its odor and taste. Acetic acid is among the least expensive organic acids, and is therefore a raw material in many commercial processes that require a carboxylic acid. Sodium acetate is one of several common salts of carboxylic acids. It is used to control the acidity of chemical processes and in preparing soaps and pharmaceutical agents. 

Allergic reactions may be trivial and local, e.g., a mild nettle-rash or hives (urticaria), or they may be general and so serious as to result in sudden death. Serious reactions are known as anaphylactic shock. Anaphylaxis can be caused by drugs (penicillin and others), horse serum, insect stings, foods (shellfish, nuts, eggs), pollen extracts, and various other agents. 

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