In terms of temperature stability, lice are in many ways similar to bed bugs: these parasites are adapted to live only in very narrow temperature ranges. Lice die at a temperature that is no longer comfortable, but still portable by humans, and therefore it is quite possible to destroy them without the use of toxic substances.
But for this we need a certain perseverance, as well as knowledge of the technology of such a fight with lice, the important nuances of which we will further consider.
Temperatures dangerous for lice
Adult lice can survive for several days at temperatures ranging from minus 5 ° C to + 40 ° C.
At temperatures beyond these values, lice and their larvae die within a few hours. At temperatures above + 54 ° C and below minus 13 ° C, the lice die within 5 minutes.
On a note
These temperatures are somewhat arbitrary.At high humidity, the temperature ranges at which lice survive are reduced, and at low humidity, they roughly correspond to the indicated values.
Already at about 0 ° C and at + 42-44 ° C, the lice are so weakened that they are easy to shake off the head or underwear. This is used in sanitation when combing lice with special combs.
These data should not be interpreted in such a way that if you walk for half an hour in the cold at minus 20 ° C without a cap, then the lice will all die at once. The hair on the human head is created by nature in order to maintain a constant temperature at the surface of the skin. So, it is there that the lice, though they feel discomfort, but they will not die for sure. Forensic scientists know that lice begin to creep away only from a corpse that has cooled down to a temperature of about 20 ° C. In other words, if the body is warm - the lice around it will survive, no matter how cold the person tormented himself.
Practice shows that it is easiest to deal with body lice with the help of heat treatment. The main place of their presence is clothing that can be boiled and hung out for several days in a hard frost. It is difficult to handle the person’s temperature critical for lice,but it is possible - even today there are specially developed methods for this, which will be discussed a little lower.
At what temperature do the nits die
Nits (lice eggs) generally more resistant to high and low temperatures. Even after exposure to deadly adult lice temperatures, the nits may not die, and after the return to normal mode, the larvae will emerge from them.
However, there are also conditions critical for louse eggs. Namely - nits die at temperatures below minus 20 ° C and above + 60 ° C. Almost instantly nits die at about 100 ° C in boiling water when boiling clothes.
Linen lice they are dangerous because if they don’t use their clothes for a long time and store them at normal positive temperatures (even if they are near zero), all adult lice on it will die of starvation, while nits will remain viable in a state of diapause. As soon as the clothes are worn by a person, warming them up, the larvae hatch out of the nits that can create a new population of parasites.
Considering reliable and strong gluing of nits to the surface, even knowing at what temperature nits die and treating fabrics with such temperature,it is impossible to completely remove them - after the destruction will require more and additional combing or cleaning clothes.
Fight against lice with frost
Knowing the temperature at which lice die, you can very effectively deal with body lice. This is usually done in winter:
- All clothes worn by the infected are hung out in the cold for several days. Desirable - for a week.
- The infected person himself is thoroughly cleaned, his head is shaved or he is carefully combed his hair with special combs.
It is important that the temperature at which things will freeze out is really very low — below minus 20 ° C. Nits die around this temperature, and after such freezing there will be no chance of survival for the parasites.
It is physically impossible to freeze the head and pubic lice without the risk for the most infected person. To combat them sometimes use other temperature methods.
High temperature lice removal
Removing lice on the body by high temperatures is quite time-consuming, 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 hair dryer blows the infected part of the body with air with a temperature of about 50 ° C, sensitive, but painless to humans.
Lice die at about 55 ° C, and at 50 ° C they lose mobility and cannot cling to hair. Accordingly, a half-hour hair treatment with such a hair dryer allows you to immobilize and weaken the parasites, after which they are shaken off and combed out from the head with special combs.
It is interesting
The idea of using a hair dryer against head lice was proposed by the British inventor Dale Clayton. Initially, he developed a remedy for head lice in the UK, but then moved to Salt Lake City, in an area with a much hotter and drier climate. There, he found that local lice are much less viable, and after staying for a long time in the sun in conditions of dry desert air, they completely lose their mobility. This encouraged him to create a special dryer.
Today, such hair dryers for mass use have not yet been released, but those who have decided to deal with lice mechanically - with the help of crests - can take a weapon into service.Before combing the hair should be washed in water with a temperature of about 55 ° C, and then dried with a regular hairdryer with the maximum tolerated temperature. Lice after this procedure will be combed out easier and in much larger quantities.
“I knew from the time I worked at the SES at what temperature lice die. It's about 50 degrees. When lice appeared in a child, I didn’t even think in the direction of any insecticides - it was all poison. I did this: I just bathe the child, then I dry his hair with a hair dryer at such a temperature, which is already a little unpleasant, but you can tolerate - about 7 minutes. Then I immediately take and comb my hair with a comb from the lice. It should be special, dense, with hard teeth. On the Internet, they are now selling a lot. Only lice and nits at this temperature do not die, but are braked, and they need to be combed over the bathtub. ”
Lyubov Ilinichna, Sterlitamak
How does temperature affect lice reproduction rates?
The rate at which the lice breed, the temperature also affects quite significantly. At temperatures below + 22 ° C and above + 40 ° C, the larvae and nymph lice stop feeding and do not develop. No nits develop at these temperatures - no larvae hatch from them,although the nits themselves do not die, their development is simply inhibited.
At the temperature at which the 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 breeding lice is + 30-32 ° C. In such conditions, the period from egg to egg is about 16-18 days. Reducing the temperature to + 28 ° C stretches this period to 23-24 days, and at + 25 ° C, it takes about 35 days from egg to egg.
At a temperature of + 22 ° C, the larvae stop hatching from nits. This is how the natural protection mechanisms of the population work - at low temperatures, lice are not viable, and it is more rational to keep dormant nits until the next warming, than to risk hatched larvae that can simply die from starvation.
Interestingly, the temperature rise at which lice livedo not lead to the opposite effect. If the temperature rise to + 34-35 ° C keeps the reproductive cycle at the level of 16-17 days, then upon reaching + 37-38 ° C, reproduction in lice generally practically stops, and after + 40 ° C they begin to die.
At the same time under natural conditions, lice in such conditions practically do not end up.
What about in nature?
Lice on a person rarely end up in 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 conditions of extreme heat, hair and clothing protect both his body and lice from significant temperature drops.
The same with animals. Human lice do not parasitize them, but they have their own analogs - lashes, very close to the lice. Due to the dense structure of the wool in animals, even in the inhabitants of the polar regions, lashing eaters of the skin itself are in quite tolerable conditions - the temperature under which the parasites can live and reproduce, remains under the dense undercoat.
In winter, under icy hairs, lashes, of course, slow down their activity a bit, but by the summer they begin to multiply at a normal speed again.
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 must be used.
How does lice infect, how is it dangerous and how to deal with parasites