Method and composition for treating pediculosis capitis
BACKGROUND OF THE INVENTION 
     The present application relates generally to the treatment of parasite infestations and, more particularly, to methods and composition to treat lice infections. 
     Pediculosis capitis (head lice) is an infestation of Pediculosis humanus, the human louse. This insect is transmitted to noninfected individuals through shared clothing and hairbrushes. Once present on the head, the adult female louse has a lifespan of about 25 days and lays up to 10 eggs each day which are attached to the hair shaft with a strong cement. Eggs hatch within 7-9 days producing more adult lice which continue the cycle. As the lice feed, they inject their digestive juices and fecal material into the skin and these &#34;bites&#34; cause pruritus. 
     In the past, chemical agents, including insecticides, have been used to treat pediculosis. These compounds include cholinesterase inhibitors such as neostigmine (Merch Index, Tenth Edition, entry no. 6311) or prostigmine (Merch Index Tenth Edition, entry no. 6311), and range from fairly toxic (thepyrethrins, Merch Index, Tenth Edition, entry no. 7865) to very toxic (lindane (Merch Index, Tenth Edition, entry no. 5329), malathion (Merch Index, Tenth Edition, entry no. 5522). All methods involve the exposure of the scalp and hair to these agents in shampoos or creams which are washed off relatively quickly. 
     While these current treatments are generally effective at killing the adult lice and eggs (nits), the dead nits remain firmly attached to the hairs after treatment. this is unsettling to the patient, as well a significant cosmetic problem. The only current means of removing dead nits is with a fine-toothed comb or forceps. These methods are time consuming and less than certain. 
     Formic acid, CH 2  O 2 , is an acid produced by ants through a distillation process. It can also be made by heating carbon monoxide and NaOH under pressure and decanting the resulting sodium formate with sulfuric acid (H 2  SO 4 ). Formic acid is a colorless liquid that is irritating to the skin. It has, however, been used in cosmetics (0.05%-0.2%) as a preservative or an astringent. 
     It has been found, surprisingly, that formic acid is useful in the treatment of pediculosis in that concentrations of formic acid from about 1% to about 25% can be used to remove dead nits from hair without producing undue damage to hair or skin. This &#34;nit removing&#34; activity of formic acid can be observed and utilized clinically either by incorporating formic acid by itself into a shampoo or rinse for use after a pediculicide preparation or by incorporating formic acid into the shampoo, lotion, or cream containing the active pediculicide. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved method of and composition for the removal of pediculosis nits (eggs) from the hair of individuals with Pediculosis capitis (head lice). The method involves single or multiple applications of shampoos, rinses, creams, or lotions containing a constitutent selected for its efficiency in dissolving the cement that holds the nits in place either immediately following treatment with a chemical pediculicide or simultaneous with the use of chemical pediculicides. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the practice of this invention formic acid is incorporated into topical products suiable for application to the hair and scalp, then applied and removed by washing after 5 to 15 minutes of contact with the hair. Products suitable for application to the hair and scalp into which formic acid may be incorporated for this use in concentrations of from 1% to 25% includes shampoos, rinses, creams, gels, lotions and solutions. Concentrations of formic acid greater than 25% are very caustic and may cause severe damage to hair and scalp. 
     Although formic acid may be utilized successfully in connection of from 1% to 25% to remove nits, the preferred range which provides effecftive removal with minimal irritant effects is from 1% to 10%. Usually a single application to the hair, left for 5 to 25 minutes, and then removed by washing is sufficient to remove all or most nits. However, additional applications may be required to remove remaining nits. The following examples illustrate the present invention. 
     EXAMPLE 1 
     A 12 year old female with Pediculosis capitis utilized a 10% agueous solution of formic acid following shampooing of her hair with lindane, an insecticide used to kill head lice. The formic acid solution was worked into the hair and allowed to remain for 5 minutes, after which it was washed off in the shower. After drying and combing the hair, none of the over 50 nits that were present before treatment remained attached to the hair. 
     EXAMPLE 2 
     Formic acid was incorporated into a commercially available creme rinse to a concentration of about 1%. Three hairs with firmly attached nits were soaked in the formic acid containing rinse for 10 minutes in a glas plate. The three hairs were then rinsed in warm water and examined after air dyring in the light. None of the hairs had a nit attached following this procedure. 
     EXAMPLE 3 
     Solutions of 1%, 5% and 25% formic acid were prepared in water and 3 different sets of three hairs to which nits (previously treated with lindane) were firmly attached were exposed to each concentration for 5 minutes each. The hairs were then washed, air dried and examined. All three nits were successfully removed from the hairs treated with 5% and 25% formic acid. One of the hairs treated in this fashion with 1% formic acid still retained a nit, while th other two hairs were nit-free. 
     EXAMPLE 4 
     Solutions of 1%, 2.5%, 5% and 25% formic acid were patch tested on the back of a 42 year female. Solutions were painted on previously marked one such by one inch areas of the back and left in place for 30 minutes before being removed. No irritation was observed in the areas treated with 1% or 2,5% formic acid; a ± erythema was noted in the patch treated area with 5% solution; a 1+ erythema was noted in the area where 25% formic acid had been applied and the subject complained of stinging and itching at that site. 
     While it is not fully understood how the formic acid accomplishes this result, it is believed that the formic acid reacts with and fractures or dissolves the cement holding the nit to the hair shaft. It is expected that other compounds may have the same effect, and any such therapeutically effective compound which loosens the nits in concentrations which are non-irritating an non-toxic to the skin and scalp may be used in the practice of this inventin. 
     While the foregoing has presented specific emodiments of the present invention, it is to be understood that these embodiments have been presented by way of example only. It is expected that other will perceive and practice variations which, though differing from the foregoing, do not depart from the spirit and scope of the invention as described and claimed herein.