How do you get bed bugs?

Adult bed bugs and their excrement

Fig. 21. Adult bed bugs and their excrement, natural size.

It may seem inexplicable, when you suddenly discover that there are bed bugs in the home. Maybe it has been some time since they were introduced.

The main reasons can be summarized as follows:

  1. The house has been visited by a person who brought them in his or her luggage.
  2. You have stayed somewhere, a hotel or hostel perhaps, where bed bugs have been, and they have then sought refuge in your luggage.
  3. They can climb in from a neighbor’s apartment. Through cracks in the panels or pipe penetration, for example.
  4. A piece of furniture with bed bugs has been introduced, maybe bought at a flea market or found in a container
  5. Bed bugs from bats, swallows or swifts can occasionally seek into the house, especially if their natural host animal is removed from the property, so the bed bugs get hungry
  6. Bed bugs do not come in from outside, they do not live freely in the Danish countryside.
  7. They are not introduced by guests if these do not carry luggage or furniture. They are only on us while they are sucking blood.
  8. They are not introduced by dogs or cats.

Physical methods

Heat treatment. All stages of insects are relatively vulnerable to high temperatures. If it rises just a few degrees above the optimum temperature, development stops and harmful effects occur. Coming up around 50 degrees Celsius the heat kills in a short time. Heat treatment is therefore an obvious control method. Less suspicious effects can be treated in an incubator for example. Just an hour at 50 degrees Celsius will suffice. Of course, it must be made sure that things get thoroughly hot during this period. Heating of rooms may be an option. Here the temperature has to be kept at 50 degrees for at least 12 hours, and attention should be paid to the fact the animals possibly will take refuge in cool crevices. The method is not without problems, and temperature sensors should in all cases be placed at strategic locations.

Cold treatment. As mentioned, bed bugs are sensitive to low temperatures. Normal deep freezer temperatures -18 to -20 degrees Celsius kill them within 3-4 days. It is a reasonable method for treating small batches of suspicious effects when it has been ensured that they can tolerate this treatment.

Non-toxic dusts. Diatomaceous earth and other fine-grained mineral soils have been used for insect control since ancient times. The “Romans” mixed fine road dust in the grain to be stored. Diatomaceous earth acts primarily by destroying the waxy layer that protects the insects from drying out. The effect is relatively slow. The insects die within a week due to water loss. In turn, this dust keeps its effects almost infinitely, if kept dry. Diatomaceous earth is suitable for treating inaccessible cavities and crevices, which can serve as strongholds for the insects.

Modified atmospheres. The principle consists in replacing the ordinary atmospheric air with an air, which is oxygen deficient and contains large amounts of nitrogen or carbon dioxide. In the long run, insects cannot live in an oxygen deficient atmosphere, but the treatment requires a lot of time, often weeks to be effective, something that requires the method to be used in fully sealed containers. Bed bugs are not particularly sensitive to nitrogen, but carbon dioxide has a direct toxic effect like heat and pressure can reduce treatment time significantly.

Biological control. Biological control where the pests’ natural enemies are actively used is a recognized method against many pests in agriculture and forestry. Bed bugs have some natural enemies, the assassin bug (page xx) among others, but their natural amount will never be such that they play a practical role, and the release of large amounts of these reduviids in Danish homes is obviously not an acceptable method of keeping bed bugs at bay.

Pesticides and methods

Cleaning. It has been mentioned that bed bugs can thrive in very clean rooms. Thorough cleaning and vacuuming can remove some of the animals, but not eradicate them completely, and if there are only a few remaining, the population will quickly grow again. However, it is obvious that it is easier to implement effective control in clean and tidy rooms.

Plant products. Historically, a variety of plant products have been used against bed bugs. Pepper, eucalyptus, mint, sweet gale, hemp, just to name a few. There is a widespread assumption that as long as a means derives from nature, it is harmless. In fact, some of the most dangerous poisons are “natural”, just mention drugs like nicotine and strychnine. The main plant insecticide has long been Pyrethrins, which are extracted from some tropical chrysanthemum species. They have many good features, they work fast, are relatively safe to use and quickly disappear from the environment again.

Synthetic insecticides. Over the years, some insecticides have been produced on the basis of the composition of pyrethrins, the synthetic pyrethroids that have been an important weapon against bed bugs. However, they have started to fail, and in 2008 a team of researchers from Aarhus University’s pest infestation laboratory showed that there is a widespread resistance to these repellents in bed bug populations.

When the first modern synthetic insecticides were introduced in the early 1940s – DDT was the first – optimism was great .A wide range of pests could now be effectively controlled, and it was relatively easy to control bed bugs. As is well known, the use of these repellents has been found a bit problematic. A resistance in insect populations quickly arose. For a long time, it was sort of possible to keep up; new types of repellents were constantly developed as resistance arose against the old ones. But in time it had become clear that these repellents have many adverse effects on people exposed to them, not to mention their effect in nature. Insecticides for use in the house have one by one been removed from the market, so that today, there are no really powerful repellents


It is probably impossible to completely guard yourself against getting bed bugs, but with some consideration, the risk can be significantly reduced.

If you have slept in a place where you have been bitten or you simply suspect bed bugs have been there, it is a good idea not to bring your luggage directly into the house. Find an appropriate place where it can be in “quarantine” and check the content before it is brought inside. Clothes may be put directly into the washing machine, or a week or so in the freezer. If the suitcase or backpack has any suspicious cavities it can be sprayed with an insecticide.
Used furniture poses a risk. The beautiful painting from the flea market or the bedside table from the container should be thoroughly checked before putting it in use.

There has been no experience with standard mosquito repellents being effectively preventive against bed bug bites.