In terms of temperature stability, lice are much like bed bugs: these parasites are adapted to live only in very narrow temperature intervals. Lice die at a temperature that is no longer comfortable, but still tolerable, and therefore destroy them without the use of poisonous substances is quite possible.
But this requires a certain perseverance, as well as a knowledge of the technology of such a fight against lice, the important nuances of which we will continue to consider.
Temperatures that are dangerous to lice
Adult lice can survive for several days at temperatures from minus 5 ° C to + 40 ° C.
At temperatures that go beyond these limits, lice and their larvae die within a few hours. At temperatures above + 54 ° C and below minus 13 ° C, lice die within 5 minutes.
On a note
These temperatures are to some extent conditional. At high humidity, the temperature ranges at which lice survive are reduced, and at low - approximately correspond to the indicated values.
Already at a temperature of about 0 ° C and at + 42-44 ° C, lice are so weak that they can be easily shaken off the head or underwear. This is used in sanitation when combing lice with special crests.
It is not necessary to interpret this data in such a way that if half an hour stroll in the cold at minus 20 ° C without a cap, then lice all at once all die. The hair covering on the person's head is created by nature in order to maintain a constant temperature at the surface of the skin. So, it is there that lice, although they feel discomfort, but do not die exactly. Forensic scientists know that lice begin to creep up only when the corpse has cooled to a temperature of about 20 ° C. In other words, if the body is warm - the lice around it will survive, no matter how much the person is tormented by the cold.
Practice shows that it is the easiest way to deal with ward lice with the help of temperature treatment. The main place of their presence is clothing that can be cooked and hung out for a few days in a hard frost. It is difficult to treat critical for lice by the temperatures of the person himself, but it is possible - for this, even today there are specially developed techniques, which will be discussed below.
At what temperature do the nests die
Nits ( louse eggs ) are generally more resistant to high and low temperatures. Even after exposure to deadly adult lice, the temperature of the nits may not die, and after returning to normal mode, larvae will be removed from them.
However, there are also critical conditions for lice eggs. Namely - nits die at a temperature below minus 20 ° C and above + 60 ° C. Almost instantly, nits perish at a temperature of about 100 ° C in steep boiling water during the digestion of clothing.
Linen lice are dangerous just because if they do not use the clothes they have infected for a long time and store it at normal positive temperatures (even if they are near-zero), all adult lice on it will die of hunger, and nits will remain viable in the state of diapause. As soon as the clothes are dressed by a person, warming it up, the larvae hatched from the nits will be able to create a new population of parasites.
Given the reliable and strong adhesion of nits to the surface, even knowing at what temperature nits are dying and treating this temperature of the tissue, it is impossible to completely remove them - after the destruction, it will also require additional combing or cleaning of clothes.
The fight against clothing lice with the help of frost
Knowing at what temperature lice die, you can very effectively fight with lice. Do this usually in winter:
- All the clothes that the infected wore are hung out in the frost for several days. It is desirable - for a week.
- The infected person is thoroughly washed, his head is shaved or the combs are carefully combed out with special combs.
It is important that the temperature at which things will freeze out is really very low - below minus 20 ° C. Nits perish at about this temperature, and after such freezing, there will be no chance for parasites to survive.
Freezing head and pubic lice is physically impossible without risk for the most infected person. To combat them, other temperature methods are sometimes used.
Lice removal by high temperatures
The excretion of lice on the body by high temperatures is quite laborious, but, as experiments show, it is quite effective.
The most revealing were the attempts of American researchers to develop a special dryer for the destruction of lice. This dryer blows the infected part of the body with air with a temperature of about 50 ° C, sensitive but painless for humans.
Lice die at a temperature of about 55 ° C, and at 50 ° C they lose mobility and can not cling to the hair. Accordingly, half-hour treatment of hair with such a hair dryer allows you to immobilize and weaken the parasites, after which they shake and comb out of the head with special combs.
It is interesting
The very idea of using a hair dryer against head lice was suggested by British inventor Dale Clayton. Initially, he developed funds from lice in the UK, but then moved to Salt Lake City, in a locality with a much hotter and drier climate. There he discovered that the local lice are much less viable, and after a long time in the sun in a dry desert air and completely lose mobility. This spodviglo him to create a special hairdryer.
Today, such hair dryers are not yet available for mass use, but those who decided to fight lice mechanically - with the help of crests - can take the method into service. Before combing out the hair, they should be washed in water with a temperature of about 55 ° C, and then dried with a normal hair dryer with the maximum tolerable temperature. Lice after this procedure will be combed out easier and in much larger quantities.
"I knew from the time of work at SES, at what temperature do louses die. It's somewhere 50 degrees. When lice appeared in the child, I did not even think of all insecticides - it's all poison. I did this: I just bathe the baby, then I dry his hair with a hair dryer at a temperature that is a bit unpleasant, but you can endure it for about 7 minutes. Then I immediately take and comb the hair with a comb from lice. It should be special, dense, with hard teeth. On the Internet, they are now selling a lot. Only lice and nits do not die at this temperature, but they are decelerated, and they need to be combed over the bathroom. "
Lyubov Ilinichna, Sterlitamak
How does the temperature affect the rate of reproduction of lice?
At the speed with which lice reproduce, the temperature also affects quite significantly. At temperatures below + 22 ° C and above + 40 ° C, larvae and nymphs of lice cease to feed and do not develop. At the same temperatures, there is no development of nits - they do not hatch larvae, although the nits themselves do not die, their development is simply inhibited.
At a temperature at which lice die, nits are still able to survive. In general, even a small change in temperature already affects the duration of the reproductive cycle of lice.
The optimal temperature for the reproduction of lice is + 30-32 ° C. Under such conditions, the period from egg to egg is about 16-18 days. Lowering the temperature to + 28 ° C stretches this period to 23-24 days, and at + 25 ° C from the egg to the egg it is already about 35 days.
At a temperature of + 22 ° C, larvae cease to hatch from the nits. So the mechanisms of natural protection of the population work - at low temperatures lice are not viable, and it is more rational to keep dormant nits before the next warming, than to risk withdrawing larvae that can simply die of hunger.
It is interesting that the increase in temperature at which lice live does not lead to the opposite effect. If the temperature rises to + 34-35 ° C, the reproductive cycle lasts at the level of 16-17 days, then at + 37-38 ° C the reproduction in lice practically stops, and after + 40 ° C they begin to die.
In this case, under natural conditions, lice under such conditions are almost not found.
And how is it in nature?
Lice on humans in general rarely get into extreme situations - thanks to their activities, people can always be in comfortable conditions for themselves and for their parasites. Even if a person is in the cold or in extreme heat, hair or clothing protects both his body and lice from significant temperature changes.
The same is true of animals. Human lice on them do not parasitize, but they have their own analogues - withers very close to lice. Due to the dense structure of wool in animals, even among the inhabitants of the polar regions, the withers near the skin turn out to be quite tolerable conditions - under a dense undercoat, a temperature is maintained at which parasites can live and reproduce.
In winter, under iced hairs, the withers, of course, slow down their activity, but by the summer they start multiplying again at normal speed.
In this respect, people are lucky - if they wish they can change their clothes, and shave their hair without the risk of being frozen or overheated. In the fight against lice, this advantage should be used.
Getting rid of lice and nits at home for 1 procedure: