It is important to remember that they have a very flat body that allows it to hide almost anywhere. During the initial onset of the infestation, they are only visible around the tufts and seams of the mattress. As the infestation grows, these bugs spread out and inhabit larger and larger areas. Generally they prefer rough surfaces like wood or paper for their harborages.
Around the time I started getting bites, I noticed more and more neighbors throwing out mattresses, furniture… I got suspicious. We live in apartments. I react differently to different kinds of bites so I can always tell the difference between mosquitoes and ants and such. I didn’t know what those bites were until I caught one of the little hellions crawling across the sheets.
Bed bugs occur around the world. Before the 1950s about 30% of houses in the United States had bedbugs. Rates of infestations in developed countries, while decreasing from the 1930s to the 1980s, have increased dramatically since the 1980s. Before the 1980s they were common in the developing world but rare in the developed world. The increase in the developed world may have been caused by increased international travel, resistance to insecticides, and the use of new pest-control methods that do not affect bed bugs.
Once you have a suspicion or a confirmed infestation, do not spread things outside of the bedroom. Don't take linens off the bed and go to sleep somewhere else—that will just move the infestation to other rooms. Ultimately pest control operators will tell you to put everything you can through the washer and dryer, since bed bugs cannot withstand high temperatures. I don't think bed bugs would be able to survive solvent-based dry cleaning, but I don't have any first-hand knowledge that that's true. Unfortunately, dry cleaners and Laundromats can be places where people pick up bed bugs. I think it's a low probability, but it only takes one adult female bed bug that has been mated to get an infestation going.
Traditional methods of repelling and/or killing bed bugs include the use of plants, fungi, and insects (or their extracts), such as black pepper; black cohosh (Actaea racemosa); Pseudarthria hookeri; Laggera alata (Chinese yángmáo cǎo | 羊毛草); Eucalyptus saligna oil; henna (Lawsonia inermis or camphire); "infused oil of Melolontha vulgaris" (presumably cockchafer); fly agaric (Amanita muscaria); tobacco; "heated oil of Terebinthina" (i.e. true turpentine); wild mint (Mentha arvensis); narrow-leaved pepperwort (Lepidium ruderale); Myrica spp. (e.g. bayberry); Robert geranium (Geranium robertianum); bugbane (Cimicifuga spp.); "herb and seeds of Cannabis"; "opulus" berries (possibly maple or European cranberrybush); masked hunter bugs (Reduvius personatus), "and many others".
The size of bed bug bites varies with a number of different factors. Bed bugs inject an anti-coagulant along with their saliva when they pierce the skin to take a blood meal. This anti-coagulant is mostly responsible for how a person reacts to the bite and determines the size of the bug’s bite. Since people will have various sensitivities to the bed bug’s bite, the size of the bite will vary, as well. Another factor that influences the size of a bed bug reaction is the number of times a person is bitten. Bite reactions of people bitten many times are also variable, and their response may be either more or less intense as the number of bites increases.